最大公约数1

执行速度（从快->慢）：__gcd()algorithm库函数>gcd更相减损术与移位结合>gcd1更相减损术>gcd2辗转相除法

#include <iostream>
#include <cstdio>
#include <climits>
#include <algorithm>
using namespace std;
//gcd更相减损术与移位结合
int gcd(int a, int b)
{
    if(a < b)
        return gcd(b, a);
    if(b == 0)
        return a;
    if(!a & 1){
        //a为b均为偶数
        if(!b & 1)
                return gcd(a >> 1, b >> 1) << 1;
            //a为偶数,b为奇数
            else 
                return gcd(a >> 1, b);
        }
        else{
            //a为奇数,b为偶数
            if(!b & 1)
                return gcd(a, b >> 1);
            //a为奇数,b为奇数
            else
                return gcd(a - b, b);
        }
}
//gcd1更相减损术
int gcd1(int a, int b){
    if(a < b)
        return gcd1(b, a);
    if(b == 0)
        return a;
    else
        return gcd1(a - b, b);
}
//gcd2辗转相除法
int gcd2(int a, int b){
    if(b == 0) return a;
    return gcd2(b, a % b);
}
int main(){
    int n;
    while(~scanf("%d", &n)){
        int maxn, minn;        
        scanf("%d", &minn);
        maxn = minn;
        for(int i = 1; i < n; i++){
            int x;
            scanf("%d", &x);
            maxn = max(maxn, x);
            minn = min(minn, x);
        }
         //printf("%d %d %d\n", minn, maxn, __gcd(minn, maxn));//使用algorithm库函数
        printf("%d %d %d\n", minn, maxn, gcd(minn, maxn));//gcd更相减损术与移位结合
        //printf("%d %d %d\n", minn, maxn, gcd1(minn, maxn));//gcd1更相减损术
        //printf("%d %d %d\n", minn, maxn, gcd2(minn, maxn));//gcd2辗转相除法
    }
    return 0;
}