最大公约数问题

#include<iostream>using namespace std;//辗转相除法求最大公约数int GCD(int x, int y){if (x<0 || y<0){return 0;}if (x<y){int tmp = 0;tmp = y;y = x;x = tmp;}return (!y)? x:GCD(y , x % y);}//不用取模方式实现int gcd(int x, int y){if (x < y)return gcd(y, x);if (y == 0)return x;elsereturn gcd(x - y, y);}//结合上述两种方法的巧妙算法int GcdPlus(int x, int y){if (x < y)return GcdPlus(y, x);if (y == 0)return x;else{if (0 == x % 2){if (0 == y % 2)return (GcdPlus(x >> 1, y >> 1) << 1);elsereturn GcdPlus(x >>1, y);}else{if (0 == y % 2)return GcdPlus(x, y >> 1);elsereturn GcdPlus(y, x - y);}}}int main(){cout << GCD(30,42) << endl;cout << gcd(42,30) << endl;cout << GcdPlus(42,30) << endl;return 0;}