BestCoder10 1001 Revenge of GCD(hdu 5019) 解题报告

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstdlib>
 4 #include <cstring>
 5 #include <algorithm>
 6 using namespace std;
 7 
 8 typedef __int64 ll;
 9 const ll maxn = 1e6 + 5;
10 ll X, Y, K, ansi;
11 ll com_factor[maxn];
12 
13 ll gcd(ll x, ll y)
14 {
15     while (y)
16     {
17         ll r = x % y;
18         x = y;
19         y = r;
20     }
21     return x;
22 }
23 
24 int main()
25 {
26     int T, cnt;
27     while (scanf("%d", &T) != EOF)
28     {
29         while (T--)
30         {
31             scanf("%I64d%I64d%I64d", &X, &Y, &K);
32             if (X < Y)
33                 swap(X, Y);
34             ll r = gcd(X, Y);
35             cnt = 0;
36             for (ll i = 1; i*i <= r; i++)
37             {
38                 if (r % i == 0)
39                 {
40                     com_factor[++cnt] = i;
41                     if (r/i != i)
42                         com_factor[++cnt] = r/i;
43                 }
44             }
45             sort(com_factor+1, com_factor+cnt+1);
46             reverse(com_factor+1, com_factor+cnt+1);
47             printf("%I64d\n", cnt < K ? -1 : com_factor[K]);
48         }
49     }
50     return 0;
51 }