Lightoj 1259 Goldbach ' s conjecture water problem

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#include <cstdio>
#include <iostream>
#include <ctime>
#include <vector>
#include <cmath>
#include <map>
#include <queue>
#include <algorithm>
#include <cstring>
using namespace std;
typedef long long LL;
const int N=1e7+5;
const int INF=0x3f3f3f3f;
int cnt;
bool v[N];
int prime[700000];
void getprime(){
  for(int i=2;i*i<=N-5;++i)
    if(!v[i])
      for(int j=i*i;j<=N-5;j+=i)
        v[j]=1;
  for(int i=2;i<=N-5;++i)
  if(!v[i])prime[++cnt]=i;
}
int main()
{
    getprime();
    int cas=0,T;
    scanf("%d",&T);
    while(T--){
      int n;
      scanf("%d",&n);
      int pos=upper_bound(prime+1,prime+1+cnt,n/2)-prime;
      int ans=0;
      for(int i=1;i<pos;++i){
        if(!v[n-prime[i]])++ans;
      }
      printf("Case %d: %d\n",++cas,ans);
    }
    return 0;
}

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Lightoj 1259 Goldbach ' s conjecture water problem