【模板小程序】求第n个质数

 1 #include <iostream>
 2 #include <vector>
 3 using namespace std;
 4 
 5 int nth_prime(int n) {
 6   vector<int> primes(n);
 7   primes[0] = 2;
 8   int CntOfPrime = 1;
 9   for (int i = 3; CntOfPrime < n; ++i) {
10     bool isPrime = true;
11     for (int j = 0; j < CntOfPrime && primes[j]*primes[j] <= i; ++j) {
12       if (i % primes[j] == 0) {
13         isPrime = false;
14         break;
15       }
16     }
17     if (isPrime) {
18       ++CntOfPrime;
19       primes[CntOfPrime - 1] = i;
20     }
21   }
22   return primes[n - 1];
23 }
24 
25 int main() {
26   int n;
27   while (cin >> n) {
28     cout << nth_prime(n) << endl;
29   }
30   return 0;
31 }