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;
}