Euler project3: the largest prime factor

问题描述：

The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?

C++:

#include<bits/stdc++.h>using namespace std;int main(){    long long n,ans=2;    cin>>n;    long long q=(long long)sqrt(n*1.0);    long long i=2;    /*     * 若正整数a>1,且a不能被不超过a的平方根的任一素数整除，     * 则a是素数     */    while(i <= q && n > 1)    {        while(n % i == 0)            {                n /= i;                ans=max(ans,i);                //cout<<ans<<endl;            }        i++;    }    cout<<ans<<endl;    return 0;}