hdu-5019 Revenge of GCD

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 const int maxn = 1e5 + 10;
 5 ll a[maxn];
 6 int main()
 7 {
 8     int T;
 9     cin >> T;
10     while(T--)
11     {
12         ll x, y, k, tot = 0;
13         scanf("%lld%lld%lld", &x, &y, &k);
14         ll g = __gcd(x, y);
15         for(ll i = 1; i * i <= g; i++)
16         {
17             if(g % i == 0)
18             {
19                 a[tot++] = i;
20                 if(i * i != g)a[tot++] = g / i;
21             }
22         }
23         if(k > tot)printf("-1\n");
24         else
25         {
26             sort(a, a + tot);
27             k = tot - k + 1;
28             printf("%lld\n", a[k - 1]);
29         }
30     }
31     return 0;
32 }