diff --git a/exercises/01_helloworld.c b/exercises/01_helloworld.c
index e6100166bcb8fd1064fc94f2bb0e1a6952ba8bd1..140adb01b19e0f064e5cc8a2c6b193afab735b2f 100644
--- a/exercises/01_helloworld.c
+++ b/exercises/01_helloworld.c
@@ -5,7 +5,7 @@ int main(){
     // Print "Hello World!" to the console
     
     
-    
+    printf("Hello World!");
 
     return 0;
 }
\ No newline at end of file
diff --git a/exercises/02_loop.c b/exercises/02_loop.c
index 3e361e61656c2d9ea05348a15fa275dcd3201b8a..34b8bb7d9a4281240aedb9d846e06f44c7d38713 100644
--- a/exercises/02_loop.c
+++ b/exercises/02_loop.c
@@ -8,6 +8,11 @@
 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..a819f4bfb7d77b50d2da5138f4c96026c3bfe5bd 100644
--- a/exercises/03_nested_loops.c
+++ b/exercises/03_nested_loops.c
@@ -12,6 +12,13 @@
 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..83c078aa1e770abf6cfc70f41759c5c7250434d4 100644
--- a/exercises/04_prime_number.c
+++ b/exercises/04_prime_number.c
@@ -11,6 +11,20 @@ int main(void)
 	for (i = 1; i <= 100; i++)
 	{
 		//TODO
+		        int is_prime = 1;
+        if (i <= 1) {
+            is_prime = 0;
+        } else {
+            for (j = 2; j * j <= i; j++) {
+                if (i % j == 0) {
+                    is_prime = 0;
+                    break;
+                }
+            }
+        }
+        if (is_prime) {
+            max = i;
+        }
 	}
 
 	printf("max = %d\n", max);
diff --git a/exercises/05_josephus_ring.c b/exercises/05_josephus_ring.c
index 330f2045f5cda70d21728503ef40accd04cea14f..138a5e6a93a01ac8b13beb4dec036d2853b93978 100644
--- a/exercises/05_josephus_ring.c
+++ b/exercises/05_josephus_ring.c
@@ -21,8 +21,26 @@ int main(void)
 	int pos;	/* 当前报数位置 */
 	int step;	/* 当前报数 */
 
-	//TODO
-	
+        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;
+                                step = 0;
+                                left--;
+                        }
+                }
+                pos = (pos + 1) % ALL_NUM;
+        }
 	
 
 	return 0;