# Maximum possible elements which are divisible by 2

• Difficulty Level : Hard
• Last Updated : 09 Feb, 2022

Given an integer array arr of size N. The task is to find the maximum possible elements in the array which are divisible by 2 after modifying the array. One can perform the below operation an arbitrary number of times(possibly zero times).

Replace any two elements in the array with their sum.

Examples:

Input : arr = [1, 2, 3, 1, 3]
Output :
After adding elements at index 0 and 2, and index 3 and 4, array becomes arr=[4, 2, 4].
Input : arr = [1, 2, 3, 4, 5]
Output :
After adding 1 and 3, array becomes arr=[4, 2, 4, 5].

Approach
First, observation is that we don’t need to modify elements that are divisible by 2(i.e., even numbers). Then we left with odd numbers. The addition of two numbers will give an even number that is divisible by 2.
So finally, the result will be:

count_even + count_odd/2.

Below is the implementation of the above approach:

## CPP

 `// CPP program to find maximum possible``// elements which divisible by 2``#include ``using` `namespace` `std;` `// Function to find maximum possible``// elements which divisible by 2``int` `Divisible(``int` `arr[], ``int` `n)``{``    ``// To store count of even numbers``    ``int` `count_even = 0;` `    ``for` `(``int` `i = 0; i < n; i++)``        ``if` `(arr[i] % 2 == 0)``            ``count_even++;` `    ``// All even numbers and half of odd numbers``    ``return` `count_even + (n - count_even) / 2;``}` `// Driver code``int` `main()``{``    ``int` `arr[] = { 1, 2, 3, 4, 5 };` `    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr[0]);` `    ``// Function call``    ``cout << Divisible(arr, n);` `    ``return` `0;``}`

## Java

 `// Java program to find maximum possible``// elements which divisible by 2``class` `GFG``{` `    ``// Function to find maximum possible``    ``// elements which divisible by 2``    ``static` `int` `Divisible(``int` `arr[], ``int` `n)``    ``{``        ``// To store count of even numbers``        ``int` `count_even = ``0``;``    ` `        ``for` `(``int` `i = ``0``; i < n; i++)``            ``if` `(arr[i] % ``2` `== ``0``)``                ``count_even++;``    ` `        ``// All even numbers and half of odd numbers``        ``return` `count_even + (n - count_even) / ``2``;``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `main (String[] args)``    ``{``        ``int` `arr[] = { ``1``, ``2``, ``3``, ``4``, ``5` `};``    ` `        ``int` `n = arr.length;``    ` `        ``// Function call``        ``System.out.println(Divisible(arr, n));``    ``}``}` `// This code is contributed by AnkitRai01`

## Python3

 `# Python3 program to find maximum possible``# elements which divisible by 2` `# Function to find maximum possible``# elements which divisible by 2``def` `Divisible(arr, n):``    ``# To store count of even numbers``    ``count_even ``=` `0` `    ``for` `i ``in` `range``(n):``        ``if` `(arr[i] ``%` `2` `=``=` `0``):``            ``count_even``+``=``1` `    ``# All even numbers and half of odd numbers``    ``return` `count_even ``+` `(n ``-` `count_even) ``/``/` `2` `# Driver code` `arr``=``[``1``, ``2``, ``3``, ``4``, ``5``]` `n ``=` `len``(arr)` `# Function call``print``(Divisible(arr, n))` `# This code is contributed by mohit kumar 29`

## C#

 `// C# program to find maximum possible``// elements which divisible by 2``using` `System;` `class` `GFG``{``    ` `    ``// Function to find maximum possible``    ``// elements which divisible by 2``    ``static` `int` `Divisible(``int` `[]arr, ``int` `n)``    ``{``        ``// To store count of even numbers``        ``int` `count_even = 0;``    ` `        ``for` `(``int` `i = 0; i < n; i++)``            ``if` `(arr[i] % 2 == 0)``                ``count_even++;``    ` `        ``// All even numbers and half of odd numbers``        ``return` `count_even + (n - count_even) / 2;``    ``}``    ` `    ``// Driver code``    ``static` `public` `void` `Main ()``    ``{``        ` `        ``int` `[]arr = { 1, 2, 3, 4, 5 };``        ``int` `n = arr.Length;``        ` `        ``// Function call``        ``Console.Write(Divisible(arr, n));``    ``}``}` `// This code is contributed by ajit.`

## Javascript

 ``

Output:

`3`

Time complexity: O(N).
Auxiliary Space: O(1).

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