From 69ea5bf488ba772858b4449e4bce6b8fd1a6fb67 Mon Sep 17 00:00:00 2001
From: osc_61505645 <8765271+wjtwgm@user.noreply.gitee.com>
Date: Sat, 4 Sep 2021 10:50:56 +0000
Subject: [PATCH] add math/qmidian.cpp. this program can find midian just need
 O(N),

---
 math/qmidian.cpp | 63 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 math/qmidian.cpp

diff --git a/math/qmidian.cpp b/math/qmidian.cpp
new file mode 100644
index 000000000..d7bec5e60
--- /dev/null
+++ b/math/qmidian.cpp
@@ -0,0 +1,63 @@
+#include<unistd.h>
+
+#include<iostream>
+using namespace std;
+template<class T>
+T get_mid(T* a, int l)
+{
+    a-=1;
+    int mid1_num,mid2_num;
+    mid1_num=1,mid2_num=2;//keep mid1num<kip2num
+    if(a[1]>a[2])
+    {
+        swap(mid1_num,mid2_num);
+    }
+    for( int i=3; i<=l; ++i)
+    {
+        if(i%2)
+        {
+            if(a[i]>a[mid1_num]&&a[i]<a[mid2_num])
+            {
+                mid1_num=a[i];
+                continue;
+            }
+            if(a[i]>a[mid2_num])
+            {
+                mid1_num=mid2_num;
+                mid2_num=i;
+                continue;
+            }
+
+        }
+        if(a[i]<a[mid1_num])
+        {
+            mid2_num=mid1_num;
+            mid1_num=i;
+            continue;
+        }
+        if(a[i]>a[mid1_num]&&a[i]<a[mid2_num])
+        {
+            mid2_num=i;
+        }
+    }
+    if(l%2==0)
+    {
+        return (a[mid2_num]+a[mid1_num])/2;
+
+    }
+
+    return a[mid1_num];
+}
+
+int main()//test main function
+{
+    int n,ans;
+    cin>>n;
+    int a[n];
+    for(int i=0; i<n; ++i)
+    {
+        cin >>a[i];
+    }
+    ans=get_mid<int>(a,n);
+    cout<<ans;
+}
-- 
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