LightOJ 1370 Bi-shoe and Phi-shoe（素数筛选法）

Bi-shoe and Phi-shoe

解题思路：

AC代码：

#include <iostream>#include <cstdio>#include <cstring>using namespace std;typedef long long ll;int unprime[1000200];void is_prime(){    memset(unprime,0,sizeof(unprime));    unprime[1] = 1;    for(int i = 2; i <= 1000100; i++){//注意临界值        int tt = 1000100/i;        for(int j = 2; j <= tt; j++){            unprime[i*j] = 1;        }    }}int main(){    is_prime();    int T,t = 1;    scanf("%d",&T);    while(T--){        int n,x;        scanf("%d",&n);        ll ans = 0;        for(int i = 0; i < n; i++){            scanf("%d",&x);            for(int j = x+1; ; j++){                if(!unprime[j]){                    ans += j;                    break;                }            }        }        printf("Case %d: %lld Xukha\n",t++,ans);    }    return 0;}