版权声明: https://blog.csdn.net/weixin_40959045/article/details/88381889
打表得
#include<bits/stdc++.h>
using namespace std;
#define fst first
#define sec second
#define sci(num) scanf("%d",&num)
#define scl(num) scanf("%lld",&num)
#define mem(a,b) memset(a,b,sizeof a)
#define cpy(a,b) memcopy(a,b,sizeof b)
typedef long long LL;
typedef pair<int,int> P;
const int MAX_N = 1e7 + 100;
const int MAX_M = 1e6;
bool isp[MAX_N];
int primes[MAX_M];
void init() {
for (int i =2 ;i < MAX_N;i++) {
if (!isp[i]) {
primes[++primes[0]] = i;
for (int j = i + i;j < MAX_N;j+= i) {
isp[j] = true;
}
}
}
}
int main() {
init();
int T;
sci(T);
for (int cs = 1;cs <= T;cs++) {
int N;sci(N);
int ans = 0;
for (int i = 1;i <= primes[i] && primes[i] <= N / 2;i++) {
if (!isp[N - primes[i]])
ans++;
}
printf("Case %d: %d\n",cs,ans);
}
return 0;
}