LightOJ 1259 Goldbach`s Conjecture(证明哥德巴赫猜想)

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <algorithm>
#include <climits>
#include <cmath>
#include <ctime>
#include <cassert>
#include <bitset>
#define IOS ios_base::sync_with_stdio(0); cin.tie(0);
using namespace std;
typedef long long ll;
const int MAX_N = 10000010;

int T, n, prime_cnt, cases = 0;
int prime[7 * MAX_N / 100];
bitset<MAX_N> bs;

void GetPrime()
{
prime_cnt = 0;
bs.set();
for(int i = 2; i < MAX_N; i++){
if(bs[i] == 1) prime[prime_cnt++] = i;
for(int j = 0; j < prime_cnt && i * prime[j] < MAX_N; j++){
bs[i * prime[j]] = 0;
if(i % prime[j] == 0) break;
}
}
//printf("prime_cnt = %d\n", prime_cnt);
}

int main()
{
GetPrime();
scanf("%d", &T);
while(T--){
scanf("%d", &n);
int num = 0;
for(int i = 0; prime[i] <= n / 2; i++){
if(bs[n - prime[i]]) num++;
}
printf("Case %d: %d\n", ++cases, num);
}
return 0;
}