小于n的素数

#include <iostream>#include <cstdio>#include <cstdlib>#include <vector>#include <map>#include <set>#include <queue>#include <stack>#include <algorithm>#include <string>#include <cstring>#include <cmath>using namespace std;const int MAX_NUM = 10000000;void PrimeFun1(){vector<int> prime;prime.reserve(MAX_NUM * 0.07);prime.push_back(2);for (int i=3; i <= MAX_NUM; i += 2){bool isPrime = true;for (int j = 0; j < prime.size() && prime[j] * prime[j] <= i; j++){if (i % prime[j] == 0){isPrime=false;break;}}if (isPrime){prime.push_back(i);}}cout << prime.size() << endl << MAX_NUM << endl << prime.size() / (double)MAX_NUM << endl;//for (int i = 0; i < prime.size(); i++)//{//cout << prime[i] << endl;//}}//better onebool isPrime[MAX_NUM+1];void PrimeFun2(){memset(isPrime,true,sizeof(isPrime));for(int i=4; i <= MAX_NUM; i+=2)isPrime[i]=false;for (int i = 3; i * i <= MAX_NUM; i += 2){if (isPrime[i]){for (int j = i * i; j <= MAX_NUM; j += i){isPrime[j] = false;}}}vector<int> prime;for (int i = 2;i <= MAX_NUM; i++){if (isPrime[i]){prime.push_back(i);}}cout << prime.size() << endl << MAX_NUM << endl << prime.size() / (double)MAX_NUM << endl;//for (int i = 0; i < prime.size(); i++)//{//cout << prime[i] << endl;//}}int main(){PrimeFun2();PrimeFun1();system("pause");return 0;}