第k大GCD = GCD／第K大因子

Revenge of GCD

3
2 3 1
2 3 2
8 16 3

1
-1
2

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>

using namespace std;

typedef long long int LL;

LL gcd(LL a,LL b)
{
    if(b==0) return a;
    return gcd(b,a%b);
}

LL factor[1000100],n;

int main()
{
    int T_T;
    scanf("%d",&T_T);
    while(T_T--)
    {
        LL x,y,k;
        cin>>x>>y>>k;
        LL g=gcd(x,y);
        LL d=sqrt(g);
        n=0;
        for(LL i=1;i<=d;i++)
        {
            if(g%i==0)
            {
                LL j=g/i;
                factor[n++]=i;
                if(j!=i) factor[n++]=j;
            }
        }
        sort(factor,factor+n);
        if(k>n) puts("-1");
        else
        {
            cout<<g/factor[k-1]<<endl;
        }
    }
    return 0;
}

HDOJ 5019 Revenge of GCD

原文：http://blog.csdn.net/ck_boss/article/details/39461065