大炮打蚊子——二进制光速GCD

我用光速GCD来做不过分吧～

AC代码：

#include <bits/stdc++.h>
using namespace std;
int n, m;

inline int gcd(int x, int y) {
    if (!x) return y;
    if (!y) return x;
    int shift = __builtin_ctz(x | y);
    x >>= __builtin_ctz(x);
    y >>= __builtin_ctz(y);
    while (x != y) {
        if (x > y) {
            swap(x, y);
        }
        y -= x;
        y >>= __builtin_ctz(y);
    }
    return x << shift;
}

int main() {
    cin >> n >> m;
    cout << gcd(n, m) << endl;
    return 0;
}