Finding prime factors

Question

#include 
using namespace std;

void whosprime(long long x)
{
    bool imPrime = true;

    for(int i = 1; i <= x; i++)
    {
        for(int z =          


        

Answer 1

A C++ implementation using @user448810's pseudocode:

#include 
using namespace std;

void factors(long long n) {
    long long z = 2;
    while (z * z <= n) {
        if (n % z == 0) {
            cout << z << endl;
            n /= z;
        } else {
            z++;
        }
    }
    if (n > 1) {
        cout << n << endl;
    }
}

int main(int argc, char *argv[]) {
    long long r = atoll(argv[1]);
    factors(r);
}

// g++ factors.cpp -o factors ; factors 600851475143

Perl implementation with the same algorithm is below.
Runs ~10-15x slower (Perl 0.01 seconds for n=600851475143)

#!/usr/bin/perl
use warnings;
use strict;

sub factors {
    my $n = shift;
    my $z = 2;
    while ($z * $z <= $n) {
        if ( $n % $z ) {
            $z++;
        } else {
            print "$z\n";
            $n /= $z;
        }
    }
    if ( $n > 1 ) {
        print "$n\n"
    }
}

factors(shift);

# factors 600851475143