最大公约数

#include <iostream>#include <cstdio>#include <cstdlib>#include <string>#include <cstring>#include <sstream>#include <cmath>#include <vector>#include <algorithm>using namespace std;int gcd(int a,int  b){    return !b?a:gcd(b,a%b);}int main(){    int a=12,b=16;    int res=gcd(a,b);    cout<<res;    return 0;}