Maximum Length of Subarray with Even Sum in C++

We are given with an array Arr[] of integers. The goal is to find longest length subarray of Arr[] , sum of whose elements is even. That is, the sum of elements of a subarray is even and that subarray is longest in length.

Input − Arr[] = { 2,3,5,2,6,7 }.

Output −Maximum length of subarray − 4

Explanation −The maximum length subarray is { 5,2,6,7 }. Sum is 20 which is even.

Input − Arr[] = { 5,7,7,3,4 }.

Output − Maximum length of subarray − 4

Explanation − The maximum length subarray is { 5,7,7,3 }. Sum is 22 which is even.

Approach used in the below program is as follows

• The integer array Arr[] is used to store the integers.

• Variable size is used to store the length of the array.

• Function Length( int arr[] ) is check the sum of arrays is even. Leng is used to store the length of subarray.

• Calculate whole sum of array, if even return length of array, n.

• Now starting from the first element, traverse the whole array, if an odd element is found then find the length of both halfs excluding arr[i].

• Return the max length for the length of the subarray.

Example

 Live Demo

#include<iostream< int Length(int arr[], int n){    int sum = 0, leng = 0;    // if whole array is even    for (int i = 0; i < n; i++)       sum += arr[i];    if (sum % 2 == 0) // total sum is already even       return n;    // Find an index i such the a[i] is odd    // and compare length of both halfs excluding    // a[i] to find max length subarray    for (int i = 0; i < n; i++) {       if (arr[i] % 2 == 1)          leng = i>n-i-1?i:n-i-1;    }    return leng; } int main(){    int Arr[] = { 1, 2, 6, 2, 4,2 };    int size = 6;    printf("Maximum length of subarray such that sum of the subarray is even: %d",Length(Arr, size)); return 0; }

Output

If we run the above code it will generate the following output −

Maximum length of subarray such that sum of the subarray is even : 5