SUBARRAY GCD

SUBGCD.cpp

#include <iostream>
using namespace std;

long long gcd(long long a, long long b){    // Find the GCD of two numbers using euclidian algorithm
    if(b==0) return a;
    return gcd(b, a%b);
}

int main(){
    long long T, N, x, g;
    cin >> T;
    while(T--){
        cin >> N;
        g = 0;                          // This is initialised to 0 because gcd(0, anything) = anything
        for(long long i=0; i<N; i++){   // Find GCD of the array of numbers using the property that gcd(a,b,c) = gcd(a, gcd(b,c))
            cin >> x;
            g = gcd(g, x);
        }

        if(g==1) cout << N << endl;     // if gcd==1, then it's always 1 for the whole array
        else cout << -1 << endl;        // else no such subarray with gcd==1 exists
    }
    return 0;
}