HackerRank# Red John is Back

原题地址

简单动归+素数判定，没用筛法也能过

代码：

 #include <cmath>
 #include <cstdio>
 #include <vector>
 #include <iostream>
 #include <algorithm>
 #include <cstring>
 using namespace std;

 #define MAX_N 64
 #define MAX_M 1000000

 int T, N;
 int cnt[MAX_N];
 int p[MAX_M];

 int is_prime(int n) {
     for (int i = ; i * i <= n; i++)
         if (n % i == )
             return ;
     return ;
 }

 int main() {
     /* Enter your code here. Read input from STDIN. Print output to STDOUT */
     p[] = ;
     for (int i = ; i < MAX_M; i++)
         p[i] = p[i - ] + is_prime(i);
     cin >> T;
     while (T--) {
         cin >> N;
         memset(cnt, , sizeof(cnt));
         cnt[] = ;
         for (int i = ; i <= N; i++)
             cnt[i] = cnt[i - ] + (i -  >=  ? cnt[i - ] : );
         cout << p[cnt[N]] << endl;
     }
     return ;
 }