1292. 哥德巴赫猜想数论 线性筛

Posted 2021-10-27 幽殇默

https://www.acwing.com/problem/content/description/1294/

#include<bits/stdc++.h>
using namespace std;
const int N=1e6+10;
int st[N],prime[N],cnt,t;
void init()
{
    int n=1e6;
    for(int i=2;i<=n;i++)
    {
        if(!st[i]) prime[cnt++]=i;
        for(int j=0;prime[j]<=n/i;j++)
        {
            st[i*prime[j]]=1;
            if(i%prime[j]==0) break;
        }
    }
}
int main(void)
{
    init();
    while(cin>>t,t)
    {
        bool flag=0;
        for(int i=0;i<cnt;i++)
        {
            if(!st[t-prime[i]])
            {
                printf("%d = %d + %d\\n",t,prime[i],t-prime[i]);
                flag=1;
                break;
            }
        }
        if(!flag) puts("Goldbach's conjecture is wrong.");
    }
    return 0;
}