【BestCoder】 HDOJ 5019 Revenge of GCD

#include <iostream>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <bitset>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 1000005
#define maxm 300005
#define eps 1e-10
#define mod 10000007
#define INF 1e9
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid
#define rson o<<1 | 1, mid+1, R
typedef long long LL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}
LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}
// head

LL p[maxn], a, b, k;
int cmp(LL a, LL b)
{
return a > b;
}
void work(void)
{
LL t = gcd(a, b), tt = sqrt(t);
int cnt = 0;
for(LL i = 1; i <= tt; i++)
if(t % i == 0) {
p[++cnt] = i;
if(i * i != t) p[++cnt] = t / i;
}
sort(p+1, p+cnt+1, cmp);
if(k > cnt) printf("-1\n");
else printf("%I64d\n", p[k]);
}
int main(void)
{
int _;
while(scanf("%d", &_)!=EOF) {
while(_--) {
scanf("%I64d%I64d%I64d", &a, &b, &k);
work();
}
}
return 0;
}