diff --git a/exercises/01_helloworld.c b/exercises/01_helloworld.c
index e6100166bcb8fd1064fc94f2bb0e1a6952ba8bd1..f040b4ed7ea28c41abdfcac208ddaa8aafcd667b 100644
--- a/exercises/01_helloworld.c
+++ b/exercises/01_helloworld.c
@@ -4,8 +4,6 @@ int main(){
 
     // Print "Hello World!" to the console
     
-    
-    
-
+    printf("Hello World!\n");  
     return 0;
 }
\ No newline at end of file
diff --git a/exercises/02_loop.c b/exercises/02_loop.c
index 3e361e61656c2d9ea05348a15fa275dcd3201b8a..9364553c31bf4871fe5c18bc073ce692bf2e5aee 100644
--- a/exercises/02_loop.c
+++ b/exercises/02_loop.c
@@ -8,6 +8,9 @@
 int main(void)
 {
 	//TODO
-
+	int i;
+    for (i = 1; i <= 10; i++) {
+        printf("%d\n", i);
+    }
 	return 0;
 }
\ No newline at end of file
diff --git a/exercises/03_nested_loops.c b/exercises/03_nested_loops.c
index d80c6903dd22e3305e35ff2bfb82f949e9975617..e19d2c4b839698e5d8f39b3c1e9afe060c0350bb 100644
--- a/exercises/03_nested_loops.c
+++ b/exercises/03_nested_loops.c
@@ -12,6 +12,17 @@
 int main(void)
 {		
 	//TODO
+	int i, j;
 
+    // 外层循环控制乘法表的行数
+    for (i = 1; i <= 9; i++) {
+        // 内层循环控制每行中的列数
+        for (j = 1; j <= i; j++) {
+            // 打印出当前列数和行数的乘积，后面跟随一个制表符
+            printf("%d*%d=%d\t", j, i, i * j);
+        }
+        // 每行结束后打印一个换行符
+        printf("\n");
+    }
 	return 0;
 }
\ No newline at end of file
diff --git a/exercises/04_prime_number.c b/exercises/04_prime_number.c
index 28e3f5f8cd5dbb074c60d947c925a13d8918234e..bef27739951afcdb19ad4a42bfe66b1816dab945 100644
--- a/exercises/04_prime_number.c
+++ b/exercises/04_prime_number.c
@@ -1,19 +1,32 @@
 #include <stdio.h>
 #include <math.h>
-
 //查找100以内的最大素数
 
+
+
 int main(void)
 {
-	int i, j;
-	int max = 0;
+ 	int i, j;
+    int max = 0;
 
-	for (i = 1; i <= 100; i++)
-	{
-		//TODO
-	}
+    for (i = 2; i <= 100; i++) // 从2开始，因为1不是素数
+    {
+        int isPrime = 1; // 假设当前数是素数
+        for (j = 2; j * j <= i; j++) // 只检查到i的平方根
+        {
+            if (i % j == 0) // 如果i能被j整除，则不是素数
+            {
+                isPrime = 0; // 标记为非素数
+                break; // 跳出内层循环
+            }
+        }
+        if (isPrime && i > max) // 如果是素数且大于当前最大素数
+        {
+            max = i; // 更新最大素数
+        }
+    }
 
-	printf("max = %d\n", max);
+    printf("max = %d\n", max); // 打印最大素数
 
-	return 0;
+    return 0;
 }
\ No newline at end of file
diff --git a/exercises/05_josephus_ring.c b/exercises/05_josephus_ring.c
index 330f2045f5cda70d21728503ef40accd04cea14f..e94051af30e3d32b73d09d73373b223fe4c603bf 100644
--- a/exercises/05_josephus_ring.c
+++ b/exercises/05_josephus_ring.c
@@ -8,22 +8,46 @@
  * 要求：输出每一个被淘汰人的编号，每淘汰一个人输出一行，格式为："%d out \n"(每输出一次换行)
 */
 
-#define ALL_NUM    	100 
-#define COUNT_NUM	3
-#define OUT_NUM		3
+#include <stdio.h>
+#define ALL_NUM     100
+#define COUNT_NUM   3
 
-/* people id array such as (1,2,3,4,5,6) */
 int people[ALL_NUM];
 
-int main(void)
-{
-	int left;	/* 剩余人数 */
-	int pos;	/* 当前报数位置 */
-	int step;	/* 当前报数 */
+int main(void) {
+    int left = ALL_NUM;    /* 剩余人数 */
+    int pos = 0;           /* 当前报数位置 */
+    int step = 0;         /* 当前报数 */
+
+    // 初始化people数组
+    for (int i = 0; i < ALL_NUM; i++) {
+        people[i] = i + 1;
+    }
+
+    // 模拟淘汰过程
+    while (left > 0) {
+        // 如果当前位置的人已经被淘汰，则跳过
+        if (people[pos] == 0) {
+            pos = (pos + 1) % ALL_NUM;
+            continue;
+        }
+
+        // 报数
+        step++;
+        if (step == COUNT_NUM) {
+            // 输出被淘汰人的编号
+            printf("%d out \n", people[pos]);
+            // 标记被淘汰
+            people[pos] = 0;
+            // 剩余人数减一
+            left--;
+            // 重置报数
+            step = 0;
+        }
 
-	//TODO
-	
-	
+        // 移动到下一个人
+        pos = (pos + 1) % ALL_NUM;
+    }
 
-	return 0;
+    return 0;
 }
\ No newline at end of file