PWD 27.01.2022 C++ Sito Eratostenesa

#include <iostream>
#include <vector>
#include <numeric>
#include <cmath>

std::vector<int> GetPrime(unsigned int n) {
    std::vector<int> ret(n - 2 + 1);
    std::iota(std::begin(ret), std::end(ret), 2);
    int sqr = sqrt(n);
    for (int i = 0; i <= sqr; i++) {
        int a = 2;
        while (ret[i] * a <= n) {
            ret.erase(std::remove(ret.begin(), ret.end(), ret[i] * a), ret.end());
            a++;
        }
    }
    return ret;
}
std::vector<int> GetPrime2(unsigned int n) {
    std::vector<int> ret;
    std::vector<bool> prime(n+1);
    int sqr = sqrt(n);
    for (int i = 2; i <=n; i++) {
        if (!prime[i]) {
            ret.push_back(i);
            if (i <= sqr) {
                int a = 2;
                while (i * a <= n) {
                    prime[i * a] = true;
                    a++;
                }
            }
        }
    }
    return ret;
}
int main()
{
    std::vector<int> a = GetPrime(100);
    std::vector<int> b = GetPrime2(100);
    for (int i = 0; i < b.size(); i++) {
        std::cout << a[i]<<" "<<b[i] << std::endl;
    }
}