欧几里得算法用来求最大公约数

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

例题：洛谷p1029

#include<iostream>

using namespace std;

#define int long long
#define endl '\n'

int x, y;
int ans;

int gcd(int x, int y)
{
    if(y == 0) return x;
    else return gcd(y, x % y);
}

signed main()
{
    ios :: sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
    cin >> x >> y;
    
    int t = x * y;
    for(int i = 1; i * i <= t; i ++ ) //i代表p,枚举p,因为pq=xy,所以q=t/i
        if(t % i == 0 && gcd(i, t / i) == x)
			ans += 2;
    if(x == y) ans -- ;
    
    cout << ans;
    return 0;
}