Hang electric brush oj title (2098)

Prime and spin-off

Subject description:

To an even split into two distinct primes, there are several demolition law?

Input

Some positive input contains an even number value is not more than 10,000, the number does not exceed 500, the case of 0, ends.

Output

Corresponding to each even output of which is split into different prime number, row for each result.

Sample Input

30 
26 
0

Sample Output

3 
2

By the answer:

#include<stdio.h>
#include<math.h>
int is_sushu(int x){         //判断是否为素数 
	if(x<=0){
		return 0;
	}
	for(int i=2;i<=sqrt(x);i++){   //如果 m 不能被 2 ~ sqrt(m)间任一整数整除，m 必定是素数 
		if(x%i==0)
	        return 0; 	
	}
	return 1; 
}
int main()
{
	int m,i,count; 
    while(~scanf("%d",&m))
    {   
        if(m==0)break;      //若遇0，则结束
		count=0;
		for(i=2;i<=m/2;i++){
       	    if(is_sushu(i)&&is_sushu(m-i)&&m-i!=i){    //m为两个素数之和 
       		    count++;
		    }
	    }	
		printf("%d\n",count);
	}  
    return 0;
}