C++ program to find length of non empty substring whose sum is even

Suppose we have an array A with n elements. We have to find the length of a non-empty subset of its elements such that their sum is even or return -1 when there is no such subset.

So, if the input is like A = [1, 3, 7], then the output will be 2, because sum of [1, 3] is 4.

Steps

To solve this, we will follow these steps −

n := size of A
for initialize i := 0, when i 
Example
Let us see the following implementation to get better understanding −
#include 
using namespace std;

int solve(vector A) {
   long n = A.size(), k = 0;
   for (long i = 0; i  A = { 1, 3, 7 };
   cout 
Input
{ 1, 3, 7 }
Output
2