gcd function in c++

                                    int gcd(int a, int b) 
{ 
    // Everything divides 0  
    if (a == 0) 
       return b; 
    if (b == 0) 
       return a; 
    // base case 
    if (a == b) 
        return a; 
    // a is greater 
    if (a > b) 
        return gcd(a-b, b); 
    return gcd(a, b-a); 
}

                                    #include <stdio.h>
int main()
{
    int t, n1, n2, gcd; 
    scanf("%d", &t); // Test Case Input
    while (t--)
    {
        scanf("%d %d", &n1, &n2);// Taking numbers input

        if (n2 > n1)
        {

            gcd = n1;
            n1 = n2;
            n2 = gcd;
        }
        while (n1 % n2 != 0)
        {
            gcd = n2;
            n2 = n1 % n2;
            n1 = gcd; 
        }
        // n2 is our gcd
        printf("GCD: %d\n", n2);
    }
    return 0;
}

                                    #include<iostream>
using namespace std;

int euclid_gcd(int a, int b) {
	if(a==0 || b==0) return 0;
	int dividend = a;
	int divisor = b;
	while(divisor != 0){
		int remainder = dividend%divisor;
		dividend = divisor;
		divisor = remainder;
	}
	return dividend;
}

int main()
{
	cout<<euclid_gcd(0,7)<<endl;
	cout<<euclid_gcd(55,78)<<endl;
	cout<<euclid_gcd(105,350)<<endl;
	cout<<euclid_gcd(350,105)<<endl;
	return 0;
}