diff --git a/exercises/01_helloworld.c b/exercises/01_helloworld.c
index e6100166bcb8fd1064fc94f2bb0e1a6952ba8bd1..0bab63fd8329c26ca392d3cb96c7a72ab62ad8e5 100644
--- a/exercises/01_helloworld.c
+++ b/exercises/01_helloworld.c
@@ -4,7 +4,7 @@ int main(){
 
     // Print "Hello World!" to the console
     
-    
+    printf("Hello World!\n");
     
 
     return 0;
diff --git a/exercises/02_loop.c b/exercises/02_loop.c
index 3e361e61656c2d9ea05348a15fa275dcd3201b8a..c3dfb2848dfa106f5f3fa6d69e353ee85104fd9b 100644
--- a/exercises/02_loop.c
+++ b/exercises/02_loop.c
@@ -8,6 +8,8 @@
 int main(void)
 {
 	//TODO
-
+	for(int i=1;i<=10;i++){
+		print("%d",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..05042a31e2b33d8ed47692f0f1f03c7cd2fad8cd 100644
--- a/exercises/03_nested_loops.c
+++ b/exercises/03_nested_loops.c
@@ -12,6 +12,12 @@
 int main(void)
 {		
 	//TODO
-
+	int i, j;
+    for (i = 1; i <= 9; i++) {
+        for (j = 1; j <= i; j++) {
+            printf("%d*%d=%d\t", j, i, i * j);
+        }
+        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..c0b0413b0eab16a57c71597db0de7bdc96bc2734 100644
--- a/exercises/04_prime_number.c
+++ b/exercises/04_prime_number.c
@@ -10,7 +10,20 @@ int main(void)
 
 	for (i = 1; i <= 100; i++)
 	{
-		//TODO
+		int is_prime = 1; // 假设当前数是素数
+        if (i <= 1) {
+            is_prime = 0; // 小于等于1的数不是素数
+        } else {
+            for (j = 2; j <= sqrt(i); j++) {
+                if (i % j == 0) {
+                    is_prime = 0; // 如果能被整除，不是素数
+                    break;
+                }
+            }
+        }
+        if (is_prime) {
+            max = i; // 更新最大素数
+        }
 	}
 
 	printf("max = %d\n", max);
diff --git a/exercises/05_josephus_ring.c b/exercises/05_josephus_ring.c
index 330f2045f5cda70d21728503ef40accd04cea14f..76493236991f7404ba8858c1d40780e3d7e8d2ff 100644
--- a/exercises/05_josephus_ring.c
+++ b/exercises/05_josephus_ring.c
@@ -22,7 +22,27 @@ int main(void)
 	int step;	/* 当前报数 */
 
 	//TODO
-	
+	// 初始化人员编号
+    for (int i = 0; i < ALL_NUM; i++) {
+        people[i] = i + 1;
+    }
+
+    left = ALL_NUM;
+    pos = 0;
+    step = 0;
+
+    while (left > 0) {
+        if (people[pos] != 0) {
+            step++;
+            if (step == COUNT_NUM) {
+                printf("%d out \n", people[pos]);
+                people[pos] = 0;  // 标记该人已被淘汰
+                step = 0;
+                left--;
+            }
+        }
+        pos = (pos + 1) % ALL_NUM;
+    }
 	
 
 	return 0;