【手撕】高效判断素数

#include<iostream>
#include<vector>
using namespace std;

// 判断素数的代码
void countPrimes(vector<int>&res,int n)
{
    vector<bool> rec(n, true);
    for (int i = 2; i*i < n; i++)
    {
        if (rec[i])
        {
            for (int j = i * i; j < n; j += i)
            {
                rec[j] = false;
            }
        }
    }
    for (int m = 2; m < n; m++)
    {
        if (rec[m])
            res.push_back(m);
    }
}

int main()
{
    vector<int> res;
    countPrimes(res, 100);
    for (auto num : res)
    {
        cout << num << endl;
    }
    return 0;
}