习题6-3 使用函数输出指定范围内的完数

 1 #include<stdio.h>
 2 
 3 int factorsum(int number);
 4 void PrintPN(int m, int n);
 5 
 6 int main(void)
 7 {
 8     int m, n;
 9 
10     scanf_s("%d %d", &m, &n);
11 
12     if (factorsum(m) == m)
13     {
14         printf("%d is a perfect number\n", m);
15     }
16 
17     if (factorsum(n) == n)
18     {
19         printf("%d is a perfect number\n", n);
20     }
21 
22     PrintPN(m, n);
23 
24     return 0;
25 }
26 
27 int factorsum(int number)
28 {
29     /*
30         所有数都包含因数1，所以因数和的初值设为1，然后从2开始判断
31     */
32     int sum = 1;                            
33     for (int i = 2; i < number; i++)
34     {
35         if (number % i == 0)
36         {
37             sum = sum + i;
38         }
39     }
40     return sum;
41 }
42 
43 void PrintPN(int m, int n)
44 {
45     int flag = 0;
46     for (int i = m; i <= n; i++)
47     {
48         if (factorsum(i) == i)
49         {
50             flag = 1;
51 
52             printf("%d = 1", i);
53             for (int j = 2; j < i; j++)
54             {
55                 if (i % j == 0)
56                 {
57                     printf(" + %d", j);
58                 }                    
59             }
60 
61             printf("\n");
62         }
63     }
64     if (flag == 0)
65     {
66         printf("No perfect number\n");
67     }
68 }