# LeetCode **Repository Path**: ranchod/LeetCode ## Basic Information - **Project Name**: LeetCode - **Description**: 算法工程师至少是一个工程师 - **Primary Language**: Unknown - **License**: Not specified - **Default Branch**: master - **Homepage**: None - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 1 - **Created**: 2020-07-29 - **Last Updated**: 2025-05-27 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README # 一个工程师的自我修养 **** 1.python解题**Leetcode? + details** 2.java解题**src/Solution? + details** 2.C++解题**CPP/Solution? + details** 4.特别部分**random** **** # 面试过 - [EggTopFloor](random/EggTopFloor.py) - **Tencent** - Machine learning Engineer - [HuffmanEncoding](random/HuffmanEncoding.py) - **Didichuxing** - Statistical Analyst - [最大公共字符串长度](random/最大公共字符串长度.py) - 字节跳动 - [素数伴侣](random/素数伴侣.py) - **HuaWei** - Machine learning Engineer - ```核心在于匈牙利算法``` - [Lru_Cache](random/Lru_Cache.py) - **360** - Deep learning Engineer - [消消乐](random/消消乐.py) - **Tencent** - Deep learning Engineer - [花匠摆花](random/花匠摆花.py) - **Tencent** - Deep learning Engineer - source from:http://codeforces.com/contest/474/problem/D - [意图相似度](random/意图相似度.py) - **阿里** - Algorithm Engineer - [数组分组问题](random/数组分组问题.py) - **携程** - Deep learning Engineer - [连乘质数和](random/连乘质数和.py) - **快手2020校招** - [binarySearchTree](random/binarySearchTree.py) - 搜索二叉树 - [文本编辑距离](random/文本编辑距离.py) - [01背包](random/01背包.py) - [完全背包](random/完全背包.py) - [多重背包](random/多重背包.py) - 三个都是一个套路，以01背包进行拓展 - [约瑟夫环问题](random/约瑟夫环问题.py) - [按递增间隔删数，直到最后只剩下一个数](random/递增间隔删数.py) - [SortAlgorithm](random/SortMethod.py) - Almost everytime such as **Alibaba、JD、Didichuxing**... - [GapCount](random/GapCount.py) - **Hp(Hewlett-Packard)** - Model Engineer - [无序数组排序（时间复杂度为O(n)）](random/无序数组排序（时间复杂度为O(n)）.py) - 蚂蚁金服 - [计数排序](random/计数排序.py) - **阿里-推荐算法工程师** - [插入排序](random/插入排序.py) - [希尔排序](random/希尔排序.py) - [归并排序](random/归并排序.py) - [堆排序](random/堆排序.py) - [切钢条](random/切钢条.py) - [切钢条](random/切分近似数组.py) - **阿里-数据智能技术架构师** *** # 数组 - [two-sum](LeetCode/LeetCode1two-sum.py) - source from:https://leetcode-cn.com/problems/two-sum/ - [container-with-most-water](LeetCode/LeetCode11container-with-most-water.py) - source from:https://leetcode-cn.com/problems/container-with-most-water/ - [3Sum](src/Solution15.java) - 左右双指针,亮点在于定义了很多提前跳出条件，在相同值跳过的条件判断中用nums[i+1]还是nums[i-1]尤为灵活 - source from:https://leetcode-cn.com/problems/3sum/ - [3Sum Closest](src/Solution16.java) - 这题和上面一题很类似，只是最好不要在多生产变量了，直接拿num[first]+num[last]+num[i]去和target比，而不要考虑差值是否大于0，很容易绕进去 - source from:https://leetcode-cn.com/problems/3sum-closest/ - [4Sum](src/Solution18.java) - source from:https://leetcode-cn.com/problems/4sum/ - [Remove Duplicates from Sorted Array](src/Solution26.java) - source from:https://leetcode-cn.com/problems/remove-duplicates-from-sorted-array/ - [Remove Element](src/Solution27.java) - source from:https://leetcode-cn.com/problems/remove-element/ - [search-in-rotated-sorted-array](LeetCode/LeetCode33search-in-rotated-sorted-array.py) - 螺旋数组二分 - source from:https://leetcode-cn.com/problems/search-in-rotated-sorted-array/ - [find-first-and-last-position-of-element-in-sorted-array](LeetCode/LeetCode34find-first-and-last-position-of-element-in-sorted-array.py) - 这个考的是二分法中的while跳出条件和left、right变化逻辑，本题是找出左右边界 - source from:https://leetcode-cn.com/problems/find-first-and-last-position-of-element-in-sorted-array/ - [Search Insert Position](src/Solution35.java) - source from:https://leetcode-cn.com/problems/search-insert-position/ - [combination-sum](src/Solution39.java) - 这题和上面这题很像，递归在for循环里面的回溯算法，把所有情况跑一遍。`画重点，求解过程中存着result 是List>的，而tmp_list是list的,需要把tmp_list再裹一层new ArrayList<>(tmp_list)再进行add` - source from:https://leetcode-cn.com/problems/combination-sum/ - [trapping-rain-water](LeetCode/LeetCode42trapping-rain-water.py) - 动态规划和栈的两种方法，很值得看一下 - source from:https://leetcode-cn.com/problems/trapping-rain-water/ - [rotate-image](LeetCode/LeetCode48rotate-image.py) - source from:https://leetcode-cn.com/problems/rotate-image/ - [jump-game](LeetCode/LeetCode55jump-game.py) - 记录上次每次可跳的最远距离 - source from:https://leetcode-cn.com/problems/jump-game/ - [MergeIntervals](LeetCode/LeetCode56MergeIntervals.py) - source from:https://leetcode-cn.com/problems/merge-intervals/ - [SpiralMatrixII](LeetCode/LeetCode59SpiralMatrixII.py) - 旋转矩阵题型，用了余数判断位置，比较亮点 - source from:https://leetcode-cn.com/problems/spiral-matrix-ii/ - [unique-paths-ii](LeetCode/LeetCode63unique-paths-ii.py) - source from:https://leetcode-cn.com/problems/unique-paths-ii/ - [sort-colors](LeetCode/LeetCode75sort-colors.py) - source from:https://leetcode-cn.com/problems/sort-colors/ - [Subsets](LeetCode/LeetCode78Subsets.py) - 这题利用了python的语言机制，很有意思 - source from::https://leetcode.com/problems/subsets/ - [word-search](LeetCode/LeetCode79word-search.py) - source from:https://leetcode-cn.com/problems/word-search/ - [largest-rectangle-in-histogram](src/Solution84.java) - source from:https://leetcode-cn.com/problems/largest-rectangle-in-histogram/ - [merge-sorted-array](LeetCode/LeetCode88merge-sorted-array.py) - [merge-sorted-array](src/Solution88.java) - source from:https://leetcode-cn.com/problems/merge-sorted-array/ - [palindrome-partitioning-ii](LeetCode/LeetCode132palindrome-partitioning-ii.py) - 状态二维dp+值一维dp - 半三角dp修正 - source from:https://leetcode-cn.com/problems/palindrome-partitioning-ii/ - [majority-element](LeetCode/LeetCode169majority-element.py) - source from:https://leetcode-cn.com/problems/majority-element/ - [product-of-array-except-self](LeetCode/LeetCode238product-of-array-except-self.py) - 两侧分别扫描一遍 - source from:https://leetcode-cn.com/problems/product-of-array-except-self/ - [move-zeroes](LeetCode/LeetCode283move-zeroes.py) - source from:https://leetcode-cn.com/problems/move-zeroes/ - [find-the-duplicate-number](LeetCode/LeetCode287find-the-duplicate-number.py) - 抽屉原理+环+快慢指针 - source from:https://leetcode-cn.com/problems/find-the-duplicate-number/ - [find-all-duplicates-in-an-array](LeetCode/LeetCode442find-all-duplicates-in-an-array.py) - 和上面一样，核心是每次对abs(nums[idx])-1的处理获得nums的index很有意思 - source from:https://leetcode-cn.com/problems/find-all-duplicates-in-an-array/ - [find-all-numbers-disappeared-in-an-array](LeetCode/LeetCode448find-all-numbers-disappeared-in-an-array.py) - nums[abs(nums[idx]) - 1] = -abs(nums[abs(nums[idx]) - 1]),两个abs保证了所有存在的idx都被置负了 - source from:https://leetcode-cn.com/problems/find-all-numbers-disappeared-in-an-array/ - [teemo-attacking](src/Solution495.java) - source from:https://leetcode-cn.com/problems/teemo-attacking/ - [SubarraySumEqualsK](LeetCode/LeetCode560SubarraySumEqualsK.py) - source from:https://leetcode-cn.com/problems/subarray-sum-equals-k/ - [shortest-unsorted-continuous-subarray](LeetCode/LeetCode581shortest-unsorted-continuous-subarray.py) - source from:https://leetcode-cn.com/problems/shortest-unsorted-continuous-subarray/ - [can-place-flowers](src/Solution605.java) - source from:https://leetcode-cn.com/problems/can-place-flowers/ - [valid-triangle-number](LeetCode/LeetCode611valid-triangle-number.py) - [valid-triangle-number](src/Solution611.java) - source from:https://leetcode-cn.com/problems/valid-triangle-number/ - [task-scheduler](LeetCode/LeetCode621task-scheduler.py) - 理解一下，出现次数最多的那个字母（出现次数-1）x时间窗口及为最小次数，剩余要考虑的是都为最多次数的字母数 - source from:https://leetcode-cn.com/problems/task-scheduler/ - [maximum-average-subarray-i](src/Solution643.java) - source from:https://leetcode-cn.com/problems/maximum-average-subarray-i/ - [largest-number-at-least-twice-of-others](src/Solution747.java) - source from:https://leetcode-cn.com/problems/largest-number-at-least-twice-of-others/ - [transpose-matrix](LeetCode/LeetCode867transpose-matrix.py) - source from:https://leetcode-cn.com/problems/transpose-matrix/ - [AdvantageShuffle](LeetCode/LeetCode870AdvantageShuffle.py) - 这道题的难点在于耗时，贪心算法即可，田忌赛马，可以看下 - source from:https://leetcode-cn.com/problems/advantage-shuffle/ - [sort-array-by-parity-ii](src/Solution922.java) - source from:https://leetcode-cn.com/problems/sort-array-by-parity-ii/ - [squares-of-a-sorted-array](src/Solution977.java) - source from:https://leetcode-cn.com/problems/squares-of-a-sorted-array/ - [add-to-array-form-of-integer](src/Solution989.java) - source from:https://leetcode-cn.com/problems/add-to-array-form-of-integer/ - [binary-prefix-divisible-by-5](src/Solution1018.java) - source from:https://leetcode-cn.com/problems/binary-prefix-divisible-by-5/ - [HeightChecker](LeetCode/LeetCode1051HeightChecker.py) - source from:https://leetcode-cn.com/problems/height-checker/ *** # 动态规划 - [regular-expression-matching](LeetCode/LeetCode10regular-expression-matching.py) - 分N种情况讨论状态转移矩阵。复杂：1、转移矩阵，2、初始化逻辑 - source from:https://leetcode-cn.com/problems/regular-expression-matching/ - [jump-game-ii](LeetCode/LeetCode45jump-game-ii.py) - source from:https://leetcode-cn.com/problems/jump-game-ii/ - [longest-palindromic-substring](LeetCode/LeetCode5longest-palindromic-substring.py) - 中心展开，从中间值往两边展开，判断展开终止点的长度 - source from:https://leetcode-cn.com/problems/longest-palindromic-substring/ - [maximum-subarray](LeetCode/LeetCode53maximum-subarray.py) - 简单递归 - source from:https://leetcode-cn.com/problems/maximum-subarray/ - [unique-paths](LeetCode/LeetCode62unique-paths.py) - source from:https://leetcode-cn.com/problems/unique-paths/ - [unique-paths-ii](LeetCode/LeetCode63unique-paths-ii.py) - [unique-paths-ii](src/Solution63.java) - 最优路径下的dp - source from:https://leetcode-cn.com/problems/unique-paths-ii/ - [minimum-path-sum](LeetCode/LeetCode64minimum-path-sum.py) - 非常基础简单的动态规划问题，适合理解动态规范的想法 - source from:https://leetcode-cn.com/problems/minimum-path-sum/ - [maximal-rectangle](src/Solution85.java) - source from:https://leetcode-cn.com/problems/maximal-rectangle/ - [gray-code](LeetCode/LeetCode89gray-code.py) - dp - source from:https://leetcode-cn.com/problems/gray-code/ - [decode-ways](LeetCode/LeetCode91decode-ways.py) - 状态转移方程式dp[i] = dp[i-1]+dp[i-2],复杂在什么时候加前项什么时候加后项，什么时候加两项，0的位置的考虑 - source from:https://leetcode-cn.com/problems/decode-ways/ - [distinct-subsequences](LeetCode/LeetCode115distinct-subsequences.py) - 和文本编辑距离的思路很像 - source from:https://leetcode-cn.com/problems/distinct-subsequences/ - [triangle](LeetCode/LeetCode120triangle.py) - source from:https://leetcode-cn.com/problems/triangle/ - [best-time-to-buy-and-sell-stock](LeetCode/LeetCode121best-time-to-buy-and-sell-stock.py) - [best-time-to-buy-and-sell-stock](src/Solution121.java) - source from:https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock/ - [best-time-to-buy-and-sell-stock-ii](LeetCode/LeetCode122best-time-to-buy-and-sell-stock-ii.py) - [best-time-to-buy-and-sell-stock-ii](src/Solution122.java) - source from:https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock-ii/ - [best-time-to-buy-and-sell-stock-iii](LeetCode/LeetCode123best-time-to-buy-and-sell-stock-iii.py) - source from:https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock-iii/ - [word-break](LeetCode/LeetCode139word-break.py) - 第一轮用的traceback，时间复杂度是n的n次方，扑gai；然后我想了下，既然可以考虑回溯，为什么不能递归，其实只要把方程：flag[j] = flag[i]+s[i:j] in wordDict 这个想到就行，这个算是是像加限制性条件的dp，比如20届拼多多校招，多多鸡砍树问题 - source from:https://leetcode-cn.com/problems/word-break/ - [maximum-product-subarray](LeetCode/LeetCode152maximum-product-subarray.py) - 需要存一个max和min，来做条件判断 - source from:https://leetcode-cn.com/problems/maximum-product-subarray/ - [dungeon-game](LeetCode/LeetCode174dungeon-game.py) - 反向递归 - source from:https://leetcode-cn.com/problems/dungeon-game/ - [best-time-to-buy-and-sell-stock-iv](LeetCode/LeetCode188best-time-to-buy-and-sell-stock-iv.py) - source from:https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock-iv/ - [house-robber](LeetCode/LeetCode198house-robber.py) - dp算法很经典的一道题 - source from:https://leetcode-cn.com/problems/house-robber/ - [house-robber-ii](LeetCode/LeetCode213house-robber-ii.py) - source from:https://leetcode-cn.com/problems/house-robber-ii/ - [maximal-square](LeetCode/LeetCode221maximal-square.py) - source from:https://leetcode-cn.com/problems/maximal-square/ - [Ugly Number II](src/Solution264.java) - source from:https://leetcode-cn.com/problems/ugly-number-ii/ - [perfect-squares](src/Solution279.java) - [perfect-squares](LeetCode/LeetCode279perfect-squares.py) - 双循环的dp，同样的思路python会超时，Java不会 - source from:https://leetcode-cn.com/problems/perfect-squares/ - [longest-increasing-subsequence](LeetCode/LeetCode300longest-increasing-subsequence.py) - [longest-increasing-subsequence](src/Solution300.java) - dp和递归理解的好题目，值得看 - source from:https://leetcode-cn.com/problems/longest-increasing-subsequence/ - [range-sum-query-immutable](LeetCode/LeetCode303range-sum-query-immutable.py) - source from:https://leetcode-cn.com/problems/range-sum-query-immutable/ - [best-time-to-buy-and-sell-stock-with-cooldown](LeetCode/LeetCode309best-time-to-buy-and-sell-stock-with-cooldown.py) - dp的高难题，代码中带完整带解题方法 - source from:https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock-with-cooldown/ - [burst-balloons](LeetCode/LeetCode312burst-balloons.py) - dp的超高难题，代码中带完整带解题方法 - source from:https://leetcode-cn.com/problems/burst-balloons/ - [coin-change](LeetCode/LeetCode322coin-change.py) - 斐波纳切动态规划 - source from:https://leetcode-cn.com/problems/coin-change/ - [counting-bits](src/Solution338.java) - source from:https://leetcode-cn.com/problems/counting-bits/ - [integer-break](LeetCode/LeetCode343integer-break.py) - source from:https://leetcode-cn.com/problems/integer-break/ - [count-numbers-with-unique-digits](LeetCode/LeetCode357count-numbers-with-unique-digits.py) - source from:https://leetcode-cn.com/problems/count-numbers-with-unique-digits/ - [split-array-largest-sum](LeetCode/LeetCode410split-array-largest-sum.py) - source from:https://leetcode-cn.com/problems/split-array-largest-sum/ - [ones-and-zeroes](LeetCode/LeetCode474ones-and-zeroes.py) - 01背包 - source from:https://leetcode-cn.com/problems/ones-and-zeroes/ - [partition-equal-subset-sum](LeetCode/LeetCode416partition-equal-subset-sum.py) - 01背包问题，这题主要考虑提前跳出条件 - source from:https://leetcode-cn.com/problems/partition-equal-subset-sum/ - [target-sum](LeetCode/LeetCode494target-sum.py) - 01背包+递归逻辑 - source from:https://leetcode-cn.com/problems/target-sum/ - [fibonacci-number](LeetCode/LeetCode509fibonacci-number.py) - source from:https://leetcode-cn.com/problems/fibonacci-number/ - [longest-palindromic-subsequence](LeetCode/LeetCode516longest-palindromic-subsequence.py) - 子序列通用双循环dp，这次因为涉及反推，所以用的是倒推法 - source from:https://leetcode-cn.com/problems/longest-palindromic-subsequence/ - [palindromic-substrings](LeetCode/LeetCode647palindromic-substrings.py) - 回文子串问题 - source from:https://leetcode-cn.com/problems/palindromic-substrings/ - [Partition to K Equal Sum Subsets](src/Solution698.java) - [Partition to K Equal Sum Subsets](LeetCode/LeetCode698Partition-to-K-Equal-Sum-Subsets.py) - 依旧是递归，区别在递归逻辑在for循环中，相当于并发了n条处理逻辑，有点像树展开 - source from:https://leetcode-cn.com/problems/partition-to-k-equal-sum-subsets/ - [delete-and-earn](LeetCode/LeetCode740delete-and-earn.py) - 核心在于bitmap+dp，与198题类似 - source from:https://leetcode-cn.com/problems/delete-and-earn/ - [length-of-longest-fibonacci-subsequence](LeetCode/LeetCode873length-of-longest-fibonacci-subsequence.py) - 字典进行递归，以后\[i,j]作为递归条件判断 - source from:https://leetcode-cn.com/problems/length-of-longest-fibonacci-subsequence/ - [valid-permutations-for-di-sequence](LeetCode/LeetCode903valid-permutations-for-di-sequence.py) - 爱奇艺2020届校招 - source from:https://leetcode-cn.com/problems/valid-permutations-for-di-sequence/ - [VideoStitching](LeetCode/LeetCode1024VideoStitching.py) - 贪心算法概念的比较好理解的一道题 - source from:https://leetcode-cn.com/problems/video-stitching/ - [n-th-tribonacci-number](src/Solution1137.java) - 最简单的dp - source from:https://leetcode-cn.com/problems/n-th-tribonacci-number/ - [longest-common-subsequence](LeetCode/LeetCode1143longest-common-subsequence.py) - 子序列双循环dp - source from:https://leetcode-cn.com/problems/longest-common-subsequence/ - [longest-arithmetic-subsequence-of-given-difference](LeetCode/LeetCode1218longest-arithmetic-subsequence-of-given-difference.py) - 记录状态，和跳跃游戏1一样 - source from:https://leetcode-cn.com/problems/longest-arithmetic-subsequence-of-given-difference/ *** # 二叉树 - [binary-tree-inorder-traversal](LeetCode/LeetCode94binary-tree-inorder-traversal.py) - 二叉树中序遍历三种写法 - source from:https://leetcode-cn.com/problems/binary-tree-inorder-traversal/ - [binary-tree-level-order-traversal](LeetCode/LeetCode102binary-tree-level-order-traversal.py) - 二叉树层序遍历，利用了队列先进先出的性质 - source from:https://leetcode-cn.com/problems/binary-tree-level-order-traversal/ - [maximum-depth-of-binary-tree](LeetCode/LeetCode104maximum-depth-of-binary-tree.py) - 二叉树深度计算，利用了递归性质 - source from:https://leetcode-cn.com/problems/maximum-depth-of-binary-tree/ - [merge-two-binary-trees](LeetCode/LeetCode617merge-two-binary-trees.py) - 二叉树合并，利用了递归性质 - source from:https://leetcode-cn.com/problems/merge-two-binary-trees/ - [diameter-of-binary-tree](LeetCode/LeetCode543diameter-of-binary-tree.py) - 结点之间的最大距离，和104题的深度一样 - source from:https://leetcode-cn.com/problems/diameter-of-binary-tree/ - [convert-bst-to-greater-tree](LeetCode/LeetCode538convert-bst-to-greater-tree.py) - 先遍历右子树的中序遍历，面试之前一定要看，易于理解递归在二叉树中的应用 - source from:https://leetcode-cn.com/problems/convert-bst-to-greater-tree/ - [invert-binary-tree](LeetCode/LeetCode226invert-binary-tree.py) - 反转树，相互对称 - source from:https://leetcode-cn.com/problems/invert-binary-tree/ - [implement-trie-prefix-tree](LeetCode/LeetCode208implement-trie-prefix-tree.py) - tire 字典实现 - source from:https://leetcode-cn.com/problems/implement-trie-prefix-tree/ - [construct-binary-tree-from-preorder-and-inorder-traversal](LeetCode/LeetCode105construct-binary-tree-from-preorder-and-inorder-traversal.py) - 360面试题，真有意思 - source from:https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/ - [serialize-and-deserialize-binary-tree](LeetCode/LeetCode297serialize-and-deserialize-binary-tree.py) - 二叉树-->list//list-->二叉树 - source from:https://leetcode-cn.com/problems/serialize-and-deserialize-binary-tree/ - [lowest-common-ancestor-of-a-binary-tree](LeetCode/LeetCode236lowest-common-ancestor-of-a-binary-tree.py) - left if right is None else right if left is None else root - source from:https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-tree/ - [lowest-common-ancestor-of-a-binary-search-tree](LeetCode/LeetCode235lowest-common-ancestor-of-a-binary-search-tree.py) - 和上面一题一摸一样 - source from:https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-search-tree/ - [unique-binary-search-trees](LeetCode/LeetCode96unique-binary-search-trees.py) - 动态规划 - source from:https://leetcode-cn.com/problems/unique-binary-search-trees/ - [symmetric-tree](LeetCode/LeetCode101symmetric-tree.py) - 层次遍历 - source from:https://leetcode-cn.com/problems/symmetric-tree/ - [validate-binary-search-tree](LeetCode/LeetCode98validate-binary-search-tree.py) - 搜索二叉树的左支<结点<右支，正好可以用中序遍历比较 - source from:https://leetcode-cn.com/problems/validate-binary-search-tree/ - [binary-tree-maximum-path-sum](LeetCode/LeetCode124binary-tree-maximum-path-sum.py) - 类似104题、543题这种递归的方式 - source from:https://leetcode-cn.com/problems/binary-tree-maximum-path-sum/ - [path-sum-iii](LeetCode/LeetCode437path-sum-iii.py) - dfs+两数之和 - source from:https://leetcode-cn.com/problems/path-sum-iii/ - [unique-binary-search-trees-ii](LeetCode/LeetCode95unique-binary-search-trees-ii.py) - 和[unique-binary-search-trees](LeetCode/LeetCode96unique-binary-search-trees.py)这题思路一样，不同的是，unique-binary-search-trees用的是dp，本题用的是递归，核心和之前一样，\[start,i]作为左树去递归，node(i)作为根，\[i+1,end]作为右树去递归 - source from:https://leetcode-cn.com/problems/unique-binary-search-trees-ii/ - [same-tree](LeetCode/LeetCode100same-tree.py) - 层序遍历改写 - source from:https://leetcode-cn.com/problems/same-tree/ - [binary-tree-zigzag-level-order-traversal](LeetCode/LeetCode103binary-tree-zigzag-level-order-traversal.py) - 层序遍历改写 - source from:https://leetcode-cn.com/problems/binary-tree-zigzag-level-order-traversal/ - [recover-binary-search-tree](LeetCode/LeetCode99recover-binary-search-tree.py) - **BST+中序遍历的结果是有序的**,`self.ans.append(root)`直接加结点，而非加值了 - source from:https://leetcode-cn.com/problems/recover-binary-search-tree/ - [house-robber-iii](LeetCode/LeetCode337house-robber-iii.py) - **基于树结构+动态规划**，可谓是花哨到极点了 - source from:https://leetcode-cn.com/problems/house-robber-iii/ - [construct-binary-tree-from-inorder-and-postorder-traversal](LeetCode/LeetCode106construct-binary-tree-from-inorder-and-postorder-traversal.py) - 和[construct-binary-tree-from-preorder-and-inorder-traversal](LeetCode/LeetCode105construct-binary-tree-from-preorder-and-inorder-traversal.py)类似 - source from:https://leetcode-cn.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/ - [construct-binary-tree-from-preorder-and-postorder-traversal](LeetCode/LeetCode889construct-binary-tree-from-preorder-and-postorder-traversal.py) - 和[construct-binary-tree-from-preorder-and-inorder-traversal](LeetCode/LeetCode105construct-binary-tree-from-preorder-and-inorder-traversal.py)类似 - source from:https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-postorder-traversal/ - [binary-tree-level-order-traversal-ii](LeetCode/LeetCode107binary-tree-level-order-traversal-ii.py) - 层次遍历翻版 - source from:https://leetcode-cn.com/problems/binary-tree-level-order-traversal-ii/ - [convert-sorted-array-to-binary-search-tree](LeetCode/LeetCode108convert-sorted-array-to-binary-search-tree.py) - 有序数组-->平衡二叉树：二分查找+递归 - source from:https://leetcode-cn.com/problems/convert-sorted-array-to-binary-search-tree/ - [balanced-binary-tree](LeetCode/LeetCode110balanced-binary-tree.py) - 判断是否为平衡二叉树，利用的是dfs+[maximum-depth-of-binary-tree](LeetCode/LeetCode104maximum-depth-of-binary-tree.py)二叉树深度计算的方法 - source from:https://leetcode-cn.com/problems/balanced-binary-tree/ - [minimum-depth-of-binary-tree](LeetCode/LeetCode111minimum-depth-of-binary-tree.py) - source from:https://leetcode-cn.com/problems/minimum-depth-of-binary-tree/ - [path-sum](LeetCode/LeetCode112path-sum.py) - source from:https://leetcode-cn.com/problems/path-sum/ - 上面这两题在return的时候都做了是否是根结点的判断:`left if root.right is None else right if root.left is None else left or right` - [path-sum-ii](LeetCode/LeetCode113path-sum-ii.py) - dfs - source from:https://leetcode-cn.com/problems/path-sum-ii/ - [flatten-binary-tree-to-linked-list](LeetCode/LeetCode114flatten-binary-tree-to-linked-list.py) - 有点技巧性 - source from:https://leetcode-cn.com/problems/flatten-binary-tree-to-linked-list/ - [populating-next-right-pointers-in-each-node](LeetCode/LeetCode116populating-next-right-pointers-in-each-node.py) - 跨结点直接的指向关系由root.next is not None产生 - source from:https://leetcode-cn.com/problems/populating-next-right-pointers-in-each-node/ - [populating-next-right-pointers-in-each-node-ii](LeetCode/LeetCode117populating-next-right-pointers-in-each-node-ii.py) - 与上一次递归不同，这一次因为不知道root对应的下一层是否有空结点，所以针对上一层的判断结果进行迭代 - source from:https://leetcode-cn.com/problems/populating-next-right-pointers-in-each-node-ii/ - [sum-root-to-leaf-numbers](LeetCode/LeetCode129sum-root-to-leaf-numbers.py) - dfs - source from:https://leetcode-cn.com/problems/sum-root-to-leaf-numbers/ - [binary-tree-preorder-traversal](LeetCode/LeetCode144binary-tree-preorder-traversal.py) - 前序遍历迭代版，技巧就是queue进栈的策略是先右后左，因为前序遍历是中左右，进栈越早出栈越晚 - source from:https://leetcode-cn.com/problems/binary-tree-preorder-traversal/ - [binary-tree-postorder-traversal](LeetCode/LeetCode145binary-tree-postorder-traversal.py) - `巧妙的解法：宽度搜索+逆序出栈==后序输出`。另外，这份代码在`node = queue.pop()`-->`node = queue.pop(0)`,加个0就是层序遍历 - source from:https://leetcode-cn.com/problems/binary-tree-postorder-traversal/ >以上两题加[binary-tree-inorder-traversal](LeetCode/LeetCode94binary-tree-inorder-traversal.py)都是迭代的解法，前序中序写的比较中规中矩，后序写的真的是惊艳 - [binary-tree-right-side-view](LeetCode/LeetCode199binary-tree-right-side-view.py) - 层序遍历 - source from:https://leetcode-cn.com/problems/binary-tree-right-side-view/ - [add-and-search-word-data-structure-design](LeetCode/LeetCode211add-and-search-word-data-structure-design.py) - Tire树很经典的一道题 - source from::https://leetcode-cn.com/problems/add-and-search-word-data-structure-design/ - [count-complete-tree-nodes](LeetCode/LeetCode222count-complete-tree-nodes.py) - source from:https://leetcode-cn.com/problems/count-complete-tree-nodes/ - [kth-smallest-element-in-a-bst](LeetCode/LeetCode230kth-smallest-element-in-a-bst.py) - source from:https://leetcode-cn.com/problems/kth-smallest-element-in-a-bst/ - [binary-search-tree-iterator](LeetCode/LeetCode173binary-search-tree-iterator.py) - 借鉴了上一题中的generation的写法，我觉得非常适合业务中真实使用 - source from:https://leetcode-cn.com/problems/binary-search-tree-iterator/ - [binary-tree-paths](LeetCode/LeetCode257binary-tree-paths.py) - dfs - source from:https://leetcode-cn.com/problems/binary-tree-paths/ - [sum-of-left-leaves](LeetCode/LeetCode404sum-of-left-leaves.py) - 限制性条件下的二叉树遍历计算查找，迭代要比计算更加高效 - source from:https://leetcode-cn.com/problems/sum-of-left-leaves/ - [serialize-and-deserialize-bst](LeetCode/LeetCode449serialize-and-deserialize-bst.py) - 前序遍历保存，二叉搜索树的中序遍历为升序列，两则可以恢复原树 - source from:https://leetcode-cn.com/problems/serialize-and-deserialize-bst/ - [delete-node-in-a-bst](LeetCode/LeetCode450delete-node-in-a-bst.py) - 看子节点的是否为None，分情况讨论 - source from:https://leetcode-cn.com/problems/delete-node-in-a-bst/ - [find-mode-in-binary-search-tree](LeetCode/LeetCode501find-mode-in-binary-search-tree.py) - 直接遍历统计 - source from:https://leetcode-cn.com/problems/find-mode-in-binary-search-tree/ - [find-bottom-left-tree-value](LeetCode/LeetCode513find-bottom-left-tree-value.py) - source from:https://leetcode-cn.com/problems/find-bottom-left-tree-value/ - [find-largest-value-in-each-tree-row](LeetCode/LeetCode515find-largest-value-in-each-tree-row.py) - source from:https://leetcode-cn.com/problems/find-largest-value-in-each-tree-row/ - [minimum-absolute-difference-in-bst](LeetCode/LeetCode530minimum-absolute-difference-in-bst.py) - source from:https://leetcode-cn.com/problems/minimum-absolute-difference-in-bst/ - [binary-tree-tilt](LeetCode/LeetCode563binary-tree-tilt.py) - source from:https://leetcode-cn.com/problems/binary-tree-tilt/ - [subtree-of-another-tree](LeetCode/LeetCode572subtree-of-another-tree.py) - 递归求解，好题目 - source from:https://leetcode-cn.com/problems/subtree-of-another-tree/ - [most-frequent-subtree-sum](LeetCode/LeetCode508most-frequent-subtree-sum.py) - 和[binary-tree-tilt](LeetCode/LeetCode563binary-tree-tilt.py)一样，计算每个结点的子树之和。 - source from:https://leetcode-cn.com/problems/most-frequent-subtree-sum/ - [add-one-row-to-tree](LeetCode/LeetCode623add-one-row-to-tree.py) - 递归直接修改树的实现，爬楼梯的翻版 - source from:https://leetcode-cn.com/problems/add-one-row-to-tree/ - [average-of-levels-in-binary-tree](LeetCode/LeetCode637average-of-levels-in-binary-tree.py) - source from:https://leetcode-cn.com/problems/average-of-levels-in-binary-tree/ - [find-duplicate-subtrees](LeetCode/LeetCode652find-duplicate-subtrees.py) - 套路总结 - source from:https://leetcode-cn.com/problems/find-duplicate-subtrees/ - [two-sum-iv-input-is-a-bst](LeetCode/LeetCode653two-sum-iv-input-is-a-bst.py) - source from:https://leetcode-cn.com/problems/two-sum-iv-input-is-a-bst/ - [maximum-binary-tree](LeetCode/LeetCode654maximum-binary-tree.py) - source from:https://leetcode-cn.com/problems/maximum-binary-tree/ - [n-ary-tree-level-order-traversal](LeetCode/LeetCode429n-ary-tree-level-order-traversal.py) - source from:https://leetcode-cn.com/problems/n-ary-tree-level-order-traversal/ - [maximum-depth-of-n-ary-tree](LeetCode/LeetCode559maximum-depth-of-n-ary-tree.py) - source from:https://leetcode-cn.com/problems/maximum-depth-of-n-ary-tree/ - [maximum-width-of-binary-tree](LeetCode/LeetCode662maximum-width-of-binary-tree.py) - source from:https://leetcode-cn.com/problems/maximum-width-of-binary-tree/ - [trim-a-binary-search-tree](LeetCode/LeetCode669trim-a-binary-search-tree.py) - 如果接一个`root = self.trimBST`相当于对结点做一个覆盖，也就是直接修改树 - source from:https://leetcode-cn.com/problems/trim-a-binary-search-tree/ - [second-minimum-node-in-a-binary-tree](LeetCode/LeetCode671second-minimum-node-in-a-binary-tree.py) - log(h)的跳出条件的递归写法 - source from:https://leetcode-cn.com/problems/second-minimum-node-in-a-binary-tree/ - [longest-univalue-path](LeetCode/LeetCode687longest-univalue-path.py) - 逻辑理解的递归 - source from:https://leetcode-cn.com/problems/longest-univalue-path/ - [n-ary-tree-preorder-traversal](LeetCode/LeetCode589n-ary-tree-preorder-traversal.py) - source from:https://leetcode-cn.com/problems/n-ary-tree-preorder-traversal/ - [n-ary-tree-postorder-traversal](LeetCode/LeetCode590n-ary-tree-postorder-traversal.py) - source from:https://leetcode-cn.com/problems/n-ary-tree-postorder-traversal/ - [search-in-a-binary-search-tree](LeetCode/LeetCode700search-in-a-binary-search-tree.py) - source from:https://leetcode-cn.com/problems/search-in-a-binary-search-tree/ - [insert-into-a-binary-search-tree](LeetCode/LeetCode701insert-into-a-binary-search-tree.py) - source from:https://leetcode-cn.com/problems/insert-into-a-binary-search-tree/ - [minimum-distance-between-bst-nodes](LeetCode/LeetCode783minimum-distance-between-bst-nodes.py) - source from:https://leetcode-cn.com/problems/minimum-distance-between-bst-nodes/ - [binary-tree-pruning](LeetCode/LeetCode814binary-tree-pruning.py) - 先递归到底层，然后在判断是否可以被修剪，修剪条件就是`root.val == 0 and not root.left and not root.right:` - source from:https://leetcode-cn.com/problems/binary-tree-pruning/ - [smallest-subtree-with-all-the-deepest-nodes](LeetCode/LeetCode865smallest-subtree-with-all-the-deepest-nodes.py) - 构造了数据对\[root,depth]，用depth判断深度，用root返回depth对应的root - source from:https://leetcode-cn.com/problems/smallest-subtree-with-all-the-deepest-nodes/ - [leaf-similar-trees](LeetCode/LeetCode872leaf-similar-trees.py) - source from:https://leetcode-cn.com/problems/leaf-similar-trees/ - [all-possible-full-binary-trees](LeetCode/LeetCode894all-possible-full-binary-trees.py) - 基于树的动态规划，考前必看 - source from:https://leetcode-cn.com/problems/all-possible-full-binary-trees/ - [increasing-order-search-tree](LeetCode/LeetCode897increasing-order-search-tree.py) - source from:https://leetcode-cn.com/problems/increasing-order-search-tree/ - [range-sum-of-bst](LeetCode/LeetCode938range-sum-of-bst.py) - source from:https://leetcode-cn.com/problems/range-sum-of-bst/ - [flip-equivalent-binary-trees](LeetCode/LeetCode951flip-equivalent-binary-trees.py) - source from:https://leetcode-cn.com/problems/flip-equivalent-binary-trees/ - [check-completeness-of-a-binary-tree](LeetCode/LeetCode958check-completeness-of-a-binary-tree.py) - 层次遍历，出现空之后不能再出现结点 - source from:https://leetcode-cn.com/problems/check-completeness-of-a-binary-tree/ - [univalued-binary-tree](LeetCode/LeetCode965univalued-binary-tree.py) - source from:https://leetcode-cn.com/problems/univalued-binary-tree/ - [distribute-coins-in-binary-tree](LeetCode/LeetCode979distribute-coins-in-binary-tree.py) - 金币题，题目有点难理解，算得是每个结点的多余量，这题和[jump-game](LeetCode/LeetCode55jump-game.py)神似 - source from:https://leetcode-cn.com/problems/distribute-coins-in-binary-tree/ - [cousins-in-binary-tree](LeetCode/LeetCode993cousins-in-binary-tree.py) - 这题是结合了父结点+子节点递归，利用depth保存层数，parent保存子结点对应的父结点 - source from:https://leetcode-cn.com/problems/cousins-in-binary-tree/ - [construct-binary-search-tree-from-preorder-traversal](LeetCode/LeetCode1008construct-binary-search-tree-from-preorder-traversal.py) - source from:https://leetcode-cn.com/problems/construct-binary-search-tree-from-preorder-traversal/ - [sum-of-root-to-leaf-binary-numbers](LeetCode/LeetCode1022sum-of-root-to-leaf-binary-numbers.py) - `^`在python里面是抑或，不是次方 - source from:https://leetcode-cn.com/problems/sum-of-root-to-leaf-binary-numbers/ - [maximum-difference-between-node-and-ancestor](LeetCode/LeetCode1026maximum-difference-between-node-and-ancestor.py) - source from:https://leetcode-cn.com/problems/maximum-difference-between-node-and-ancestor/ - [delete-nodes-and-return-forest](LeetCode/LeetCode1110delete-nodes-and-return-forest.py) - 复杂的dfs，在dfs的过程中对树进行修正和保存，有点难 - source from:https://leetcode-cn.com/problems/delete-nodes-and-return-forest/ - [lowest-common-ancestor-of-deepest-leaves](LeetCode/LeetCode1123lowest-common-ancestor-of-deepest-leaves.py) - source from:https://leetcode-cn.com/problems/lowest-common-ancestor-of-deepest-leaves/ - [recover-a-tree-from-preorder-traversal](LeetCode/LeetCode1028recover-a-tree-from-preorder-traversal.py) - hashmap存结点，每次更新 - source from:https://leetcode-cn.com/problems/recover-a-tree-from-preorder-traversal/ *** # 深度遍历 - [number-of-islands](LeetCode/LeetCode200number-of-islands.py) - 回溯/DFS - source from:https://leetcode-cn.com/problems/number-of-islands/ - [increasing-subsequences](src/Solution491.java) - [increasing-subsequences](LeetCode/LeetCode491increasing-subsequences.py) - source from:https://leetcode-cn.com/problems/increasing-subsequences/ - [generate-parentheses](LeetCode/LeetCode22generate-parentheses.py) - dfs - source from:https://leetcode-cn.com/problems/generate-parentheses/ - [combination-sum](LeetCode/LeetCode39combination-sum.py) - dfs，组合题型1 - source from:https://leetcode-cn.com/problems/combination-sum/ - [combination-sum-ii](LeetCode/LeetCode40combination-sum-ii.py) - dfs，组合题型2，index>start保证了双跳跃逻辑，很nice - source from:https://leetcode-cn.com/problems/combination-sum-ii/ - [subsets-ii](LeetCode/LeetCode90subsets-ii.py) - dfs，全排列升级版 - source from:https://leetcode-cn.com/problems/subsets-ii/ - [combination-sum-iii](LeetCode/LeetCode216combination-sum-iii.py) - dfs，组合题型3 - source from:https://leetcode-cn.com/problems/combination-sum-iii/ - [permutation-sequence](LeetCode/LeetCode60permutation-sequence.py) - dfs,当迭代轮数超过一次完整循环的值的时候，直接跳过 - source from:https://leetcode-cn.com/problems/permutation-sequence/ - [combinations](LeetCode/LeetCode77combinations.py) - source from:https://leetcode-cn.com/problems/combinations/ - [coin-change-2](LeetCode/LeetCode518coin-change-2.py) - dfs - source from:https://leetcode-cn.com/problems/coin-change-2/ *** # 栈 - [Valid Parentheses](src/Solution20.java) - source from:https://leetcode-cn.com/problems/valid-parentheses/ - [evaluate-reverse-polish-notation](LeetCode/LeetCode150evaluate-reverse-polish-notation.py) - 栈，亮点在python 中对负数取整数部分如何操作 - source from:https://leetcode-cn.com/problems/evaluate-reverse-polish-notation/ - [min-stack](LeetCode/LeetCode155min-stack.py) - 辅助栈，不需要排序，仅需要知道当前最小即可 - source from:https://leetcode-cn.com/problems/min-stack/ - [decode-string](LeetCode/LeetCode394decode-string.py) - 出入栈题，有点难想到 - source from:https://leetcode-cn.com/problems/decode-string/ - [daily-temperatures](LeetCode/LeetCode739daily-temperatures.py) - source from:https://leetcode-cn.com/problems/daily-temperatures/ - [remove-all-adjacent-duplicates-in-string](src/Solution1047.java) - source from:https://leetcode-cn.com/problems/remove-all-adjacent-duplicates-in-string/ *** # 二分搜索 - [divide-two-integers](src/Solution29.java) - 位运算 - source from:https://leetcode-cn.com/problems/divide-two-integers/ - [powx-n](LeetCode/LeetCode50powx-n.py) - 最简单的递归，和快排，斐波纳切数列一致的写法 - source from:https://leetcode-cn.com/problems/powx-n/ - [Searcha2DMatrixII](LeetCode/Leetcode240Searcha2DMatrixII.py) - 这题其实可以从右上角开始查找，会更快 - source from::https://leetcode.com/problems/search-a-2d-matrix-ii/ - [IntersectionofTwoArrays](LeetCode/LeetCode349IntersectionofTwoArrays.py) - source from:https://leetcode-cn.com/problems/intersection-of-two-arrays/ - [split-array-largest-sum](LeetCode/LeetCode410split-array-largest-sum.py) - 二分搜索，亮点在分组最大和变成了原数组的`[max(原数组),sum(原数组))` - source from:https://leetcode-cn.com/problems/split-array-largest-sum/ - [binary-search](LeetCode/LeetCode704binary-search.py) - source from:https://leetcode-cn.com/problems/binary-search/ *** # 回溯 - [Letter Combinations of a Phone Number](src/Solution17.java) - [LetterCombinationsofaPhoneNumber](LeetCode/LeetCode17LetterCombinationsofaPhone.py) - 这题用了dp和递归两种方法，dp更好理解也很Pythonic，递归则更加通用 - 盖题递归位置在循环中，很有意思 - source from:https://leetcode-cn.com/problems/letter-combinations-of-a-phone-number/ - [permutations](src/Solution46.java) - 递归 - source from:https://leetcode-cn.com/problems/permutations/ - [permutations-ii](LeetCode/LeetCode47permutations-ii.py) - 简单的回溯算法 - source from:https://leetcode-cn.com/problems/permutations-ii/ - [palindrome-partitioning](src/Solution131.java) - 地址和值；已经用ansValue用的是内存地址，时刻在变，所以要new ArrayList(ansValue)固定值使其不变 - 回溯的剔除； - source from:https://leetcode-cn.com/problems/palindrome-partitioning/ - [additive-number](LeetCode/LeetCode306additive-number.py) - source from:https://leetcode-cn.com/problems/additive-number/ - [split-array-into-fibonacci-sequence](LeetCode/LeetCode842split-array-into-fibonacci-sequence.py) - source from:https://leetcode-cn.com/problems/split-array-into-fibonacci-sequence/ - [palindrome-pairs](LeetCode/LeetCode336palindrome-pairs.py) - source from:https://leetcode-cn.com/problems/palindrome-pairs/ *** # 链表 - [AddTwoNumbers](LeetCode/LeetCode2AddTwoNumbers.py) - source from:https://leetcode-cn.com/problems/add-two-numbers/ - [remove-nth-node-from-end-of-list](LeetCode/LeetCode19remove-nth-node-from-end-of-list.py) - 链表很经典的一道题 - source from::https://leetcode-cn.com/problems/remove-nth-node-from-end-of-list/ - [Merge Two Sorted Lists](src/Solution21.java) - source from:https://leetcode-cn.com/problems/merge-two-sorted-lists/ - [Swap Nodes in Pairs](src/Solution24.java) - 递归算法，讲的很详细，递归复习专用 - 该题递归在函数中间位置，很有意思 - source from:https://leetcode-cn.com/problems/swap-nodes-in-pairs/ - [RemoveLinkedListElements](LeetCode/LeetCode203RemoveLinkedListElements.py) - 协助理解链表里面的head = head, head.next = head.next.next - source from:https://leetcode-cn.com/problems/remove-linked-list-elements/ - [reverse-linked-list](src/Solution206.java) - 递归在中间,简单题，对比上面的24题可以对比着看 - source from:https://leetcode-cn.com/problems/reverse-linked-list/ - [reverse-nodes-in-k-group](LeetCode/LeetCode25reverse-nodes-in-k-group.py) - 翻转链表用的是迭代，参考206题reverse-linked-list - 交换参考的是24题Swap Nodes in Pairs - source from:https://leetcode-cn.com/problems/reverse-nodes-in-k-group/ - 深入理解地址和值 - [palindrome-linked-list](LeetCode/LeetCode234palindrome-linked-list.py) - source from:https://leetcode-cn.com/problems/palindrome-linked-list/ - [linked-list-cycle](LeetCode/LeetCode141linked-list-cycle.py) - 快慢指针，类似题型[find-the-duplicate-number](LeetCode/LeetCode287find-the-duplicate-number.py) - source from:https://leetcode-cn.com/problems/linked-list-cycle/ - [linked-list-cycle-ii](LeetCode/LeetCode142linked-list-cycle-ii.py) - 快慢指针，类似题型[find-the-duplicate-number](LeetCode/LeetCode287find-the-duplicate-number.py) - source from:https://leetcode-cn.com/problems/linked-list-cycle-ii/ - [intersection-of-two-linked-lists](LeetCode/LeetCode160intersection-of-two-linked-lists.py) - source from:https://leetcode-cn.com/problems/intersection-of-two-linked-lists/ - 短链表+长链表<-->长链表+短链表，同等初始的结尾即为交点 - [sort-list](LeetCode/LeetCode148sort-list.py) - source from:https://leetcode-cn.com/problems/sort-list/ - 并归排序+链表 - [merge-k-sorted-lists](LeetCode/LeetCode23merge-k-sorted-lists.py) - source from:https://leetcode-cn.com/problems/merge-k-sorted-lists/ - 和上一个很像，并归排序+链表 - 快排按照标值二分，小的在前大的在后，而归并则是按照下标二分，再分别对两个部分归并排序，先分后和，在和的过程中排序 - [rotate-list](LeetCode/LeetCode61rotate-list.py) - source from:https://leetcode-cn.com/problems/rotate-list/ - [remove-duplicates-from-sorted-list-ii](LeetCode/LeetCode82remove-duplicates-from-sorted-list-ii.py) - source from:https://leetcode-cn.com/problems/remove-duplicates-from-sorted-list-ii/ - 建立一个哨兵指针，每次对比cur和cur.next的val是否一致 - [remove-duplicates-from-sorted-list](LeetCode/LeetCode83remove-duplicates-from-sorted-list.py) - source from:https://leetcode-cn.com/problems/remove-duplicates-from-sorted-list/ - 上面一条的简单版本 - [partition-list](LeetCode/LeetCode86partition-list.py) - source from:https://leetcode-cn.com/problems/partition-list/ - [reverse-linked-list-ii](LeetCode/LeetCode92reverse-linked-list-ii.py) - source from:https://leetcode-cn.com/problems/reverse-linked-list-ii/ - prev.next为反转后的尾结点，正好可以接剩余结点，非常精彩 - [convert-sorted-list-to-binary-search-tree](LeetCode/LeetCode109convert-sorted-list-to-binary-search-tree.py) - source from:https://leetcode-cn.com/problems/convert-sorted-list-to-binary-search-tree/ - 反转链表[reverse-linked-list](src/Solution206.java) + 平衡二叉树[balanced-binary-tree](LeetCode/LeetCode110balanced-binary-tree.py) - [reorder-list](LeetCode/LeetCode143reorder-list.py) - source from:https://leetcode-cn.com/problems/reorder-list/ - 反转链表[reverse-linked-list](src/Solution206.java) - [insertion-sort-list](LeetCode/LeetCode147insertion-sort-list.py) - source from:https://leetcode-cn.com/problems/insertion-sort-list/ - 这题和[remove-duplicates-from-sorted-list-ii](LeetCode/LeetCode82remove-duplicates-from-sorted-list-ii.py)类似，需要不停的从head结点找到比当前结点.next.val要小的结点位置 - 链表删结点方法 - [delete-node-in-a-linked-list](LeetCode/LeetCode237delete-node-in-a-linked-list.py) - source from:https://leetcode-cn.com/problems/delete-node-in-a-linked-list/ - 一行但是非常技巧 - [odd-even-linked-list](LeetCode/LeetCode328odd-even-linked-list.py) - source from:https://leetcode-cn.com/problems/odd-even-linked-list/ - [add-two-numbers-ii](LeetCode/LeetCode445add-two-numbers-ii.py) - source from:https://leetcode-cn.com/problems/add-two-numbers-ii/ - 双栈+链表 - [split-linked-list-in-parts](LeetCode/LeetCode725split-linked-list-in-parts.py) - source from:https://leetcode-cn.com/problems/split-linked-list-in-parts/ - [flatten-a-multilevel-doubly-linked-list](LeetCode/LeetCode430flatten-a-multilevel-doubly-linked-list.py) - source from:https://leetcode-cn.com/problems/flatten-a-multilevel-doubly-linked-list/ - [linked-list-components](LeetCode/LeetCode817linked-list-components.py) - source from:https://leetcode-cn.com/problems/linked-list-components/ - [linked-list-components](LeetCode/LeetCode817linked-list-components.py) - source from:https://leetcode-cn.com/problems/linked-list-components/ - [middle-of-the-linked-list](LeetCode/LeetCode876middle-of-the-linked-list.py) - source from:https://leetcode-cn.com/problems/middle-of-the-linked-list/ - [next-greater-node-in-linked-list](LeetCode/LeetCode1019next-greater-node-in-linked-list.py) - source from:https://leetcode-cn.com/problems/next-greater-node-in-linked-list/ - 栈 - [remove-zero-sum-consecutive-nodes-from-linked-list](LeetCode/LeetCode1171remove-zero-sum-consecutive-nodes-from-linked-list.py) - source from:https://leetcode-cn.com/problems/remove-zero-sum-consecutive-nodes-from-linked-list/ - 前缀和+递归，面试前必看 *** # 堆 - [kth-largest-element-in-an-array](LeetCode/LeetCode215kth-largest-element-in-an-array.py) - 加速的地方在于，维护好容量为k的小根堆之后，只需要保证根堆的根结点最小即可。`min_heap(k_min, k, 0)` - source from:https://leetcode-cn.com/problems/kth-largest-element-in-an-array/ - [sliding-window-maximum](LeetCode/LeetCode239sliding-window-maximum.py) - 双端队列题目，用队列保留一个递减序列 - source from:https://leetcode-cn.com/problems/sliding-window-maximum/ - [top-k-frequent-elements](LeetCode/LeetCode347top-k-frequent-elements.py) - 求最大：小根堆；求最小：大根堆。因为只需要保证最大最小的k个值在堆内即可，无需遍历堆。 根堆输出的时候，每次交换根堆根结点到最后，小根堆的化，数组越靠后越小，相当于降序排列；大根堆的话，数组越往后越大，相当于升序排列。 - source from:https://leetcode-cn.com/problems/top-k-frequent-elements/ - [DistantBarcodes](LeetCode/LeetCode1054DistantBarcodes.py) - source from:https://leetcode-cn.com/problems/distant-barcodes/ *** # 双指针 - [LongestSubstringWithoutRepeatingCharacters](LeetCode/LeetCode3LongestSubstringWithoutRepeatingCharacters.py) - 滑动窗口 - source from:https://leetcode-cn.com/problems/longest-substring-without-repeating-characters/ - [boats-to-save-people](src/Solution881.java) - 双指针 - source from:https://leetcode-cn.com/problems/boats-to-save-people/ - [fruit-into-baskets](src/Solution904.java) - 双指针 - source from:https://leetcode-cn.com/problems/fruit-into-baskets/ - [minimum-window-substring](LeetCode/LeetCode76minimum-window-substring.py) - 双指针+滑动窗口，模板要记得 - source from:https://leetcode-cn.com/problems/minimum-window-substring/ - [is-subsequence](LeetCode/LeetCode392is-subsequence.py) - 双指针+滑动窗口，模板要记得 - source from:https://leetcode-cn.com/problems/is-subsequence/ - [minimum-size-subarray-sum](LeetCode/LeetCode209minimum-size-subarray-sum.py) - 子集问题，双指针 - source from:https://leetcode-cn.com/problems/minimum-size-subarray-sum/ - [longest-chunked-palindrome-decomposition](LeetCode/LeetCode1147longest-chunked-palindrome-decomposition.py) - 回文问题，双指针 - source from:https://leetcode-cn.com/problems/longest-chunked-palindrome-decomposition/ - [shortest-palindrome](LeetCode/LeetCode214shortest-palindrome.py) - 回文问题，双指针 - source from:https://leetcode-cn.com/problems/shortest-palindrome/ - [replace-the-substring-for-balanced-string](LeetCode/LeetCode1234replace-the-substring-for-balanced-string.py) - 最优子串，双指针 - source from:https://leetcode-cn.com/problems/replace-the-substring-for-balanced-string/ *** # 字符串 - [Roman to Integer](src/Solution13.java) - source from:https://leetcode-cn.com/problems/roman-to-integer/ - [Longest Common Prefix](src/Solution14.java) - source from:https://leetcode-cn.com/problems/longest-common-prefix/ - [detect-capital](LeetCode/LeetCode520detect-capital.py) - source from:https://leetcode-cn.com/problems/detect-capital/ - [custom-sort-string](LeetCode/LeetCode791custom-sort-string.py) - source from:https://leetcode-cn.com/problems/custom-sort-string/ - [goat-latin](LeetCode/LeetCode824goat-latin.py) - source from:https://leetcode-cn.com/problems/goat-latin/ - [orderly-queue](LeetCode/LeetCode899orderly-queue.py) - 有点冒泡排序的意思 - source from:https://leetcode-cn.com/problems/orderly-queue/ - [ReverseOnlyLetters](LeetCode/LeetCode917ReverseOnlyLetters.py) - source from:https://leetcode-cn.com/problems/reverse-only-letters/ - [longest-uncommon-subsequence-i](CPP/Solution521.cpp) - source from:https://leetcode-cn.com/problems/longest-uncommon-subsequence-i/ - [longest-continuous-increasing-subsequence](CPP/Solution674.cpp) - source from:https://leetcode-cn.com/problems/longest-continuous-increasing-subsequence/ *** # 递归 - [K-thSymbolinGrammar](LeetCode/LeetCode779K-thSymbolinGrammar.py) - [K-th Symbol in Grammar](src/Solution779.java) - python用了最简单的递归表示，把结果表示出来再做，比较慢,所以加了@functools.lru_cache(maxsize=128, typed=False)对结果进行缓存 - source from:https://leetcode-cn.com/problems/k-th-symbol-in-grammar/ - [valid-tic-tac-toe-state](LeetCode/LeetCode794valid-tic-tac-toe-state.py) - 直接罗列全情况，排除一下就行 - source from:https://leetcode-cn.com/problems/valid-tic-tac-toe-state/ - [valid-palindrome-ii](LeetCode/LeetCode680valid-palindrome-ii.py) - source from:https://leetcode-cn.com/problems/valid-palindrome-ii/ *** # 蓄水池抽样 - [random-pick-index](LeetCode/LeetCode398random-pick-index.py) - 蓄水池抽烟，randint(0,cnt)控制了每次被抛弃的概率为1/(1+cnt） - source from:https://leetcode-cn.com/problems/random-pick-index/ - [linked-list-random-node](LeetCode/LeetCode382linked-list-random-node.py) - source from:https://leetcode-cn.com/problems/linked-list-random-node/ *** # 数学 - [reverse Integera](src/Solution7.java) - source from:https://leetcode-cn.com/problems/reverse-integer/ - [Palindrome Number](src/Solution9.java) - source from:https://leetcode-cn.com/problems/palindrome-number/ - [ExcelSheetColumnNumber](LeetCode/LeetCode171ExcelSheetColumnNumber.py) - source from:https://leetcode-cn.com/problems/excel-sheet-column-number/ - [UglyNumber](LeetCode/LeetCode263UglyNumber.py) - source from:https://leetcode-cn.com/problems/ugly-number/ - [reach-a-number](src/Solution754.java) - source from:https://leetcode-cn.com/problems/reach-a-number/ - [ChalkboardXORGame](LeetCode/LeetCode810ChalkboardXORGame.py) - 逻辑鬼才的题目 - source from:https://leetcode-cn.com/problems/chalkboard-xor-game/ - [LargestTriangleArea](LeetCode/LeetCode812LargestTriangleArea.py) - 任给三点，三角形面积等于abs(x1*(y2-y3)+x2*(y3-y1)+x3*(y1-y2))/2 - source from:https://leetcode-cn.com/problems/largest-triangle-area/ - [consecutive-numbers-sum](LeetCode/LeetCode829consecutive-numbers-sum.py) - (n-m)(n+m+1)=2N,a=n-m,b=n+m+1,a+b=2n+1,b-a=2m+1,所以a*b=2N,a,b一奇一偶 - source from:https://leetcode-cn.com/problems/consecutive-numbers-sum/ - [surface-area-of-3d-shapes](LeetCode/LeetCode892surface-area-of-3d-shapes.py) - 透视图角度 - source from:https://leetcode-cn.com/problems/surface-area-of-3d-shapes/ - [greatest-common-divisor-of-strings](LeetCode/LeetCode1071greatest-common-divisor-of-strings.py) - gcd，最大公约数；辗转相除法复习 - source from:https://leetcode-cn.com/problems/greatest-common-divisor-of-strings/ - [prime-palindrome](LeetCode/LeetCode866prime-palindrome.py) - 素数+回文 - source from:https://leetcode-cn.com/problems/prime-palindrome/ - [find-the-closest-palindrome](LeetCode/LeetCode564find-the-closest-palindrome.py) - 罗列情况 - source from:https://leetcode-cn.com/problems/find-the-closest-palindrome/ - [repeated-substring-pattern](LeetCode/LeetCode459repeated-substring-pattern.py) - 2N-2>N - source from:https://leetcode-cn.com/problems/repeated-substring-pattern/ *** # 位运算 - [SingleNumber](LeetCode/LeetCode136SingleNumber.py) - 这题有数学解法和位解法两种，都很值得看一下 - source from:https://leetcode.com/problems/single-number/description/ - [single-number-ii](src/Solution176.java) - [single-number-ii](LeetCode/LeetCode176single-number-ii.py) - 知识点1：设计一个逻辑运算，使满足存在两个变量a和b，当遍历nums的时候，对于重复元素x，第一次碰到x的时候，我们会将x赋给a，第二次碰到后再赋给b，第三次则全量抵消 - 知识点2：x&~x=0 - source from:https://leetcode-cn.com/problems/single-number-ii/ - [reverse-bits](LeetCode/LeetCode190reverse-bits.py) - source from:https://leetcode-cn.com/problems/reverse-bits/ - [sum-of-two-integers](src/Solution371.java) - source from:https://leetcode-cn.com/problems/sum-of-two-integers/ - [hamming-distance](LeetCode/LeetCode461hamming-distance.py) - source from:https://leetcode-cn.com/problems/hamming-distance/ *** # 哈希表 - [JewelsandStones](LeetCode/LeetCode771JewelsandStones.py) - source from:https://leetcode-cn.com/problems/jewels-and-stones/ - [find-all-anagrams-in-a-string](LeetCode/LeetCode438find-all-anagrams-in-a-string.py) - 滑动窗口去解决字符串匹配问题 - source from:https://leetcode-cn.com/problems/find-all-anagrams-in-a-string/ - [distribute-candies](LeetCode/LeetCode575distribute-candies.py) - [distribute-candies](src/Solution575.java) - source from:https://leetcode-cn.com/problems/distribute-candies/ - [uncommon-words-from-two-sentences](src/Solution884.java) - source from:https://leetcode-cn.com/problems/uncommon-words-from-two-sentences/ - [substring-with-concatenation-of-all-words](LeetCode/LeetCode30substring-with-concatenation-of-all-words.py) - hash对比 - source from:https://leetcode-cn.com/problems/substring-with-concatenation-of-all-words/ - [longest-harmonious-subsequence](LeetCode/LeetCode594longest-harmonious-subsequence.py) - source from:https://leetcode-cn.com/problems/longest-harmonious-subsequence/ - [number-of-matching-subsequences](LeetCode/LeetCode792number-of-matching-subsequences.py) - source from:https://leetcode-cn.com/problems/number-of-matching-subsequences/ *** # 贪心算法 - [candy](LeetCode/LeetCode135candy.py) - 转转2020届校招 - 分发糖果，左右各扫一遍取max - source from:https://leetcode-cn.com/problems/candy/ - [queue-reconstruction-by-height](LeetCode/LeetCode406queue-reconstruction-by-height.py) - 原题说的是前面大于等于当前身高的，所以插矮个子不会影响排序 - source from:https://leetcode-cn.com/problems/queue-reconstruction-by-height/ - [two-city-scheduling](src/Solution1029.java) - source from:https://leetcode-cn.com/problems/two-city-scheduling/ - [LemonadeChange](LeetCode/LeetCode860LemonadeChange.py) - source from:https://leetcode-cn.com/problems/lemonade-change/ *** # 分治算法 - [beautiful-array](LeetCode/LeetCode932beautiful-array.py) - [beautiful-array](src/Solution932.java) - source from:https://leetcode-cn.com/problems/beautiful-array/ *** # 桶排序 - [maximum-gap](LeetCode/LeetCode164maximum-gap.py) - 分桶，亮点在于分N+1个桶，保证一定有一个空桶，空桶的存在保证最大间隔在桶之间，不需要再去比桶内值 - source from:https://leetcode-cn.com/problems/maximum-gap/ *** # 其他 - [NimGame](LeetCode/LeetCode292NimGame.py) - 规律题，数学归纳 - source from:https://leetcode-cn.com/problems/nim-game/ - [LexicographicalNumbers](LeetCode/LeetCode386LexicographicalNumbers.py) - 字典排序，用了python特性，也同时整理基础概念，值得去看 - source from:https://leetcode-cn.com/problems/lexicographical-numbers/ - [IncreasingTripletSubsequence](LeetCode/LeetCode334IncreasingTripletSubsequence.py) - such that arr[i] < arr[j] < arr[k] given 0 ≤ i < j < k ≤ n-1 else return false,其中只要保证固定住最小和最大，不断降低最小值的下限，使得比最小值要大的值可以尽可能的接近最小值，从而更容易找到比接近最小值的值 - source from:https://leetcode-cn.com/problems/increasing-triplet-subsequence/ - [relative-ranks](src/Solution506.java) - source from:https://leetcode-cn.com/problems/relative-ranks/ - [largest-number](LeetCode/LeetCode179largest-number.py) - 这题技巧题，理解sorted中的cmp和key的作用，key是sorted元素判断依据的接受入口，而接收值需要调用functools中的cmp_to_key进行包装，python2不用这么复杂 - source from:https://leetcode-cn.com/problems/largest-number/ - [lru-cache](LeetCode/LeetCode146lru-cache.py) - source from:https://leetcode-cn.com/problems/lru-cache/