diff --git a/pset7/3-getDigit.c b/pset7/3-getDigit.c
index e566478..46ed434 100644
--- a/pset7/3-getDigit.c
+++ b/pset7/3-getDigit.c
@@ -1,16 +1,25 @@
-#include <stdio.h>
+// #include <stdio.h>
+// 
+// int getDigit(long long n);
+// 
+// int main() {
+//   long long n;
+//   int len;
+// 
+//   scanf("%lld", &n);
+//   len = getDigit(n);
+//   if (len > 1)
+//     printf("The integer %lld has %d digits.\n", n, len);
+//   else
+//     printf("The integer %lld has %d digit.\n", n, 1);
+//   return 0;
+// }
 
-int getDigit(long long n);
-
-int main() {
-  long long n;
-  int len;
-
-  scanf("%lld", &n);
-  len = getDigit(n);
-  if (len > 1)
-    printf("The integer %lld has %d digits.\n", n, len);
-  else
-    printf("The integer %lld has %d digit.\n", n, 1);
-  return 0;
+int getDigit(long long n) {
+  int len = 0;
+  while (n > 0) {
+    n /= 10;
+    len++;
+  }
+  return len;
 }
diff --git a/pset7/4-reverseNum.c b/pset7/4-reverseNum.c
new file mode 100644
index 0000000..eb8649b
--- /dev/null
+++ b/pset7/4-reverseNum.c
@@ -0,0 +1,21 @@
+// #include <stdio.h>
+// 
+// int reverseNum(int num);
+// 
+// int main() {
+//   int num;
+// 
+//   scanf("%d", &num);
+//   printf("The reverse form of number %d is %d.\n", num, reverseNum(num));
+// 
+//   return 0;
+// }
+
+int reverseNum(int num) {
+  int ans = 0;
+  while (num > 0) {
+    ans = ans * 10 + num % 10;
+    num /= 10;
+  }
+	return ans;
+}
diff --git a/pset7/5-myPow.c b/pset7/5-myPow.c
new file mode 100644
index 0000000..ebff7c5
--- /dev/null
+++ b/pset7/5-myPow.c
@@ -0,0 +1,20 @@
+// #include <stdio.h>
+// 
+// int mypow(int, int);
+// 
+// int main() {
+//   int x, n;
+// 
+//   scanf("%d%d", &x, &n);
+//   printf("%d\n", mypow(x, n));
+// 
+//   return 0;
+// }
+
+int mypow(int a, int b) {
+  int pow = 1;
+  for (int i = 0; i < b; i++) {
+    pow *= a;
+  }
+  return pow;
+}
diff --git a/pset7/6-triangle.c b/pset7/6-triangle.c
new file mode 100644
index 0000000..a85230f
--- /dev/null
+++ b/pset7/6-triangle.c
@@ -0,0 +1,59 @@
+// #include <stdio.h>
+//
+// int judgeTriangle(int, int, int);
+//
+// int main() {
+//   int a, b, c;
+//
+//   scanf("%d%d%d", &a, &b, &c);
+//
+//   switch (judgeTriangle(a, b, c)) {
+//   case -1:
+//     printf("It is not a triangle.\n");
+//     break;
+//   case 0:
+//     printf("It is a scalenous triangle.\n");
+//     break;
+//   case 1:
+//     printf("It is a right-angled triangle.\n");
+//     break;
+//   case 2:
+//     printf("It is an isosceles triangle.\n");
+//     break;
+//   case 3:
+//     printf("It is a equilateral triangle.\n");
+//     break;
+//   }
+//
+//   return 0;
+// }
+
+int judgeTriangle(int a, int b, int c) {
+  // First we bubble sort them.
+  int tmp;
+  if (a > b) {
+    tmp = a;
+    a = b;
+    b = tmp;
+  }
+  if (b > c) {
+    tmp = b;
+    b = c;
+    c = tmp;
+  }
+
+  // If this is a triangle
+  if (a + b <= c) {
+    return -1; // Not a triangle
+  } else if (b == c || a == b || a == c) {
+    if (a == b && b == c) {
+      return 3; // Equilateral
+    } else {
+      return 2; // Isosceles
+    }
+  } else if (a * a + b * b == c * c) {
+    return 1; // Right triangle
+  } else {
+    return 0;
+  }
+}
diff --git a/pset7/7-perfect.c b/pset7/7-perfect.c
new file mode 100644
index 0000000..fae0576
--- /dev/null
+++ b/pset7/7-perfect.c
@@ -0,0 +1,45 @@
+// #include <stdio.h>
+// 
+// //判断一个数是否为完全数的函数
+// int isPerfect(int);
+// 
+// //打印完全数的函数
+// void printPerfact(int);
+// 
+// int main() {
+//   int i, a, b, count;
+// 
+//   scanf("%d%d", &a, &b);
+//   count = 0; // a,b两数间完全数的数量，初始化为0
+//   for (i = a; i <= b; i++) {
+//     if (isPerfect(i)) //如果是完全数
+//     {
+//       printPerfact(i); //打印该完全数
+//       count++;         //计数器加1
+//     }
+//   }
+//   printf("The total number is %d.\n", count); //输出a,b两数间完全数的数量
+//   return 0;
+// }
+
+//判断一个数是否为完全数的函数
+int isPerfect(int n) {
+  int sum = 0;
+  for (int i = 1; i <= n / 2; i++) {
+    if (n % i == 0) {
+      sum += i;
+    }
+  }
+  return (sum == n) ? 1 : 0;
+}
+
+//打印完全数的函数
+void printPerfact(int n) {
+  printf("%i=1", n);
+  for (int i = 2; i <= n / 2; i++) {
+    if (n % i == 0) {
+      printf("+%i", i);
+    }
+  }
+  printf("\n");
+}