算法16---数论2---亲密数

  1 /*  2     题目：亲密数  3     author taoliu——alex  2016.10  4   5     主要实现两种  6     1 判断两个数是不是亲密数。  7     2 找出一定范围内的亲密数。  8   9 */ 10  11  12 #include <stdio.h> 13 #include <stdlib.h> 14  15 int  friendnum(int a,int b); 16 int factor_sum(int n); 17 void scope_friendnum(int scope); 18  19 //判断两个数是不是亲密数。 20  21 int  friendnum(int a,int b) 22 { 23     if (a==b) 24     { 25         return -1; 26     } 27     int a_sum=0; 28     int b_sum=0; 29     a_sum=factor_sum(a); 30     b_sum=factor_sum(b); 31     //printf("the factor sum of %d is %d\n",a,a_sum); 32     //printf("the factor sum of %d is %d\n",b,b_sum); 33     if ((a_sum==b)&&(b_sum==a)) 34     { 35         return 1; 36     } 37     else 38     { 39         return 0; 40     } 41  42 } 43  44 int factor_sum(int n) 45 { 46     int sum=0; 47     for (int i = 1; i < n/2+1; i++) 48     { 49         if (n%i==0) 50         { 51             sum=sum+i; 52         } 53     } 54     return sum; 55 } 56  57 // 找出一定范围内的亲密数。 58 void scope_friendnum(int scope) 59 { 60     for (int i = 1; i < scope; i++) 61     { 62         for (int j = i; j < scope; j++) 63         { 64             int ans=friendnum(i,j); 65             if(ans==1) 66                 printf("%d and %d is friendnum\n",i,j); 67         } 68     } 69 } 70  71  72 int main() 73 { 74     int judge; 75     int a,b,scope; 76     printf("what you want to do :  0 means judge two number is friendnum or not;\n"); 77     printf(" 1 means you want to find the friendnum in scope\n"); 78     //fflush(stdin); 79     scanf("%d",&judge); 80     if (judge==0) 81     { 82         printf("input two number you want to judge!\n"); 83         //fflush(stdin); 84         scanf("%d%d",&a,&b); 85         int ans=friendnum(a, b); 86         if (ans==1) 87         { 88             printf("%d and %d is friendnum\n",a,b); 89         } 90         if (ans==0) 91         { 92             printf("%d and %d is not friendnum\n",a,b); 93         } 94         else 95             printf("%d and %d is the same number ,error!\n", a,b); 96     } 97     if (judge==1) 98     { 99         printf("input the scope you want to find\n");100         //fflush(stdin);101         scanf("%d",&scope);102         scope_friendnum(scope);103     }104     return 0;105 }