素数筛 uva 543

Posted 2020-08-23 HelloWorld!--By-MJY

给你一个n求出n由2个奇质因子的和  这2个因子差最大

没有就输出‘Goldbach‘s conjecture is wrong.

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<vector>
#include<math.h>

using namespace std;
#define MAXN 1000010
bool pri[MAXN];

int main()
{
    memset(pri,0,sizeof(pri));

    for(int i=2;i<=1000;i++)
    {
        if(!pri[i])
            for(int j=i*i;j<=MAXN;j=j+i)
                pri[j]=1;
    }
    int n;

    while(scanf("%d",&n)!=EOF&&n)
    {
        int a=n/2,i;
        for(i=3;i<=a;i++)
            if(!pri[i]&&!pri[n-i])
            {
                printf("%d = %d + %d\n",n,i,n-i);
                break;
            }
        if(i>a)
            printf("‘Goldbach‘s conjecture is wrong.\n");
    }

    return 0;
}