完美數

Problem Description
An integer number is said to be a perfect number if its factors, including 1 (but not the number itself), sum to the number. For example, 6 is a perfect number because 6=1+2+3. Write a function perfect that determines if parameter number is a perfect number.
請勿用暴力破解
ex:
if(input<100)
printf("6 28 is perfect number\n");
Input Format
大於10的整數
Output Format
Print all the perfect numbers with the format “X is perfect number”.
Sample Input
100
Sample Output
6 28 is perfect number

1. #include <stdio.h>  
2. #include <stdlib.h>  
3. int isperfect(int val);  
4. int main(int argc, char *argv[]) {  
5.     int number,i;  
6.     scanf("%d",&number);  
7.     for (i=1;i<number;i++){  
8.         if(isperfect(i))  
9.         printf("%d ",i);  
10.           
11.     }  
12.     printf("is perfect number\n");  
13.     system("PAUSE");  
14.     return 0;  
15. }  
16. int isperfect(int val)  
17. {  
18.  int i;  
19.  int sum = 0;  
20.  for (i = 1; i <= val/2; i++)  
21.   if(val % i == 0)  
22.    sum += i;  
23.   
24.   
25.  if(sum == val)  
26.   return 1;  
27.  else  
28.  return 0;  
29.     
30. }