HDU 5019 - Revenge of GCD

题意

思路

代码

#include <cstdio>

#include <algorithm>

#include <functional>

#include <stack>

#include <set>

#include <iostream>

#include <string>

#include <vector>

#include <queue>

#include <cstring>

#include <string>

#include <sstream>

#include <map>

#include <cmath>

#define LL long long

#define lowbit(x) ((x) & (-x))

#define MP(a, b) make_pair(a, b)

#define MS(arr, num) memset(arr, num, sizeof(arr))

#define PB push_back

#define ROP freopen("input.txt", "r", stdin);

const double PI = acos(-1.0);

const int INF = 0x3f3f3f3f;

using namespace std;

const int MAXN = 1000 + 5;

int cnt;

vector<LL> ve;

int main()

{

//ROP;

int T;

cin >> T;

while (T--)

{

ve.clear();

LL a, b, k;

cin >> a >> b >> k;

LL ans = __gcd(a, b);

ve.push_back(1ll);

if (ans != 1) ve.push_back(ans);

for (LL i = 2; i <= (LL)sqrt(ans * 1.0); i++)

    {

int t = ans % i;

if (t == 0)

{

ve.PB(i);

if (ans / i != i) ve.PB(ans / i);

}

}

if (k > ve.size()) cout << "-1" << endl;

else

    {

nth_element(ve.begin(), ve.begin() + k - 1, ve.end(), greater<LL>());

cout << ve[k - 1] << endl;

}

}

return 0;

}