QUESTION

You are given an array A1,A2…AN. You have to tell how many pairs (i, j) exist such that 1<= i < j <= N and Ai XOR Aj is odd.\n\nInput and Output \n\nFirst line T, the number of test cases. Each test case: first line N, followed by N integers in next line. For each test case, print the required answer in one line.\n\nConstraints \n1<= T <= 10 \n1 <= N <= 10^5 \n0 <= Ai <= 10^9.

ANSWER

#include <iostream>
using namespace std;
int main()
{
    int t;
    std::cin>>t;
    while(t--)
    {
        long long n;
        std::cin>>n;
        long long arr[n];
        for(int i=0;i<n;i++)
        {
            std::cin>>arr[i];
        }
        long long o=0,e=0;
        for(int i=0;i<n;i++)
        {
            if(arr[i]%2==0)
            {
                e++;
            }
            else
            {
                o++;
            }
        }
        std::cout<<o*e<<"\n";
    }
    return 0;
}