【Difference Between Primes HDU - 4715】【素数筛法打表+模拟】

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std; 
const int maxn = 1e6 + 10;
int prime[maxn];
bool isprime[maxn];
int init()
{
    memset(prime, 0, sizeof(prime));
    isprime[0] = isprime[1] = false;
    for(int i = 2; i <= maxn; i++)
        isprime[i] = true;
    int cnt = 0;
    for(int i = 2; i <= maxn; i++)
    {
        if(isprime[i])
        {
            for(int j = i * 2; j <= maxn; j += i)
                isprime[j] = false;
            prime[cnt++] = i;
        }
    }
    return cnt;
}

int T, n;
int main()
{
    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);
    int cnt = init();
    scanf("%d", &T);
    while(T--)
    {
        scanf("%d", &n);
        int sign = 0, flag = 0;
        if(n < 0)
        {
            n = -n;
            sign = 1;
        }
        for(int i = 0; i < cnt; i++)
        {
            if(n + prime[i] < maxn - 10 && isprime[n + prime[i]])
            {
                flag = 1;
                if(sign)
                    printf("%d %d\n", prime[i], n + prime[i]);
                else 
                    printf("%d %d\n", prime[i] + n, prime[i]);
                break;
            }
        }
        if(!flag)
            printf("FAIL\n");
    }
}