# Count Even sum | HCL coding question

You are given an array arr of size N and you are provided with a number K. You have to pick K consecutive elements from the array arr, check if their sum is even, and make a count on every even sum. If K consecutive elements have an even sum, then print the count of even sums, otherwise print -1.

Input Format:

The input consists of three lines:

• The first line contains an integer N denoting the size of the array.
• The second line contains N space-separated integers denoting the elements of the array arr .
• The third line contains an integer K.

The input will be read from the STDIN by the candidate

Output Format:

if K consecutive elements have an even sum then print the count of even sums, otherwise print -1. The output will be matched to the candidate's output printed on the STDOUT

Example:

Input:

5

2 4 6 8 10

2

Output:

4

Explanation:

Since K=2, pairs having even sum are (2,4), (4,6), (6,8), and (8,10). Hence, the answer is 4.

C++ Code:-

#include <bits/stdc++.h>
using namespace std;

int main()
{
int n;
cin>>n;
int a[n];
for(int i=0;i<n;i++)
cin>>a[i];
int k;
cin>>k;
int count=0;
for(int i=0;i<n-k+1;i++)
{
int sum=0;
for(int j=i;j<i+k;j++)
{
sum+=a[j];
}
if(sum%2==0)
count++;
}
if(count==0)
cout<<"-1"<<endl;
else
cout<<count;

return 0;
}

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