# Sort all even numbers in the Array without changing order of odd elements

• Difficulty Level : Basic
• Last Updated : 11 Nov, 2021

Given an array arr[] of size N, the task is to sort all the even numbers in the array, without changing the order of odd elements
Examples:

Input: arr[] = {4, 7, 2, 11, 15}
Output: {2, 7, 4, 11, 15}
Explanation: Even numbers are sorted at their corresponding places, without changing the order of odd elements

Input: arr[] = {12, 6}
Output: {6, 12}

Approach: The task can be solved by segregating the even elements into another container say ‘evens‘, sort this container, and while iterating the array, replace the even elements with the sorted even elements stored in evens

Below is the implementation of the above approach:

## C++

 `#include ``using` `namespace` `std;` `// Function to get the required array``void` `solve(``int` `arr[], ``int` `n)``{` `    ``// Store even elements``    ``vector<``int``> evens;``    ``for` `(``int` `i = 0; i < n; i++) {``        ``if` `(arr[i] % 2 == 0)``            ``evens.push_back(arr[i]);``    ``}` `    ``// Sort all even elements``    ``sort(evens.begin(), evens.end());``    ``int` `l = 0;` `    ``// Placing even elements in sorted order``    ``for` `(``int` `i = 0; i < n; i++) {``        ``if` `(arr[i] % 2 == 0)``            ``arr[i] = evens[l++];``    ``}` `    ``// Updated array``    ``for` `(``int` `i = 0; i < n; i++)``        ``cout << arr[i] << ``" "``;``}` `// Driver Code``int` `main()``{``    ``int` `N = 5;``    ``int` `arr[N] = { 4, 7, 2, 11, 15 };``    ``solve(arr, N);``    ``return` `0;``}`

## Java

 `// Java program for the above approach``import` `java.util.*; ` `public` `class` `GFG {` `    ``// Function to get the required array``    ``static` `void` `solve(``int` `[]arr, ``int` `n)``    ``{`` ` `        ``// Store even elements``        ``ArrayList evens = ``new` `ArrayList();``        ``for` `(``int` `i = ``0``; i < n; i++) {``            ``if` `(arr[i] % ``2` `== ``0``)``                ``evens.add(arr[i]);``        ``}`` ` `        ``// Sort all even elements``        ``Collections.sort(evens); ` `        ``int` `l = ``0``;``        ` `        ``// Placing even elements in sorted order``        ``for` `(``int` `i = ``0``; i < n; i++) {``            ``if` `(arr[i] % ``2` `== ``0``)``                ``arr[i] = evens.get(l++);``        ``}`` ` `        ``// Updated array``        ``for` `(``int` `i = ``0``; i < n; i++)``            ``System.out.print(arr[i] + ``" "``);``    ``}` `    ``// Driver function``    ``public` `static` `void` `main(String []args)``    ``{``        ``int` `N = ``5``;``        ``int` `[]arr = { ``4``, ``7``, ``2``, ``11``, ``15` `};``        ``solve(arr, N);``        ` `    ``}``}` `// This code is contributed by AnkThon`

## Python3

 `# python program of the above approach` `# Function to get the required array``def` `solve(arr, n):` `        ``# Store even elements``    ``evens ``=` `[]``    ``for` `i ``in` `range``(``0``, n):``        ``if` `(arr[i] ``%` `2` `=``=` `0``):``            ``evens.append(arr[i])` `        ``# Sort all even elements``    ``evens.sort()``    ``l ``=` `0` `    ``# Placing even elements in sorted order``    ``for` `i ``in` `range``(``0``, n):``        ``if` `(arr[i] ``%` `2` `=``=` `0``):``            ``arr[i] ``=` `evens[l]``            ``l ``+``=` `1` `        ``# Updated array``    ``for` `i ``in` `range``(``0``, n):``        ``print``(arr[i], end``=``" "``)` `# Driver Code``if` `__name__ ``=``=` `"__main__"``:` `    ``N ``=` `5``    ``arr ``=` `[``4``, ``7``, ``2``, ``11``, ``15``]``    ``solve(arr, N)` `    ``# This code is contributed by rakeshsahni`

## C#

 `// C# program for the above approach``using` `System;``using` `System.Collections.Generic;` `class` `GFG {` `    ``// Function to get the required array``    ``static` `void` `solve(``int` `[]arr, ``int` `n)``    ``{`` ` `        ``// Store even elements``        ``List<``int``> evens = ``new` `List<``int``>();``        ``for` `(``int` `i = 0; i < n; i++) {``            ``if` `(arr[i] % 2 == 0)``                ``evens.Add(arr[i]);``        ``}`` ` `        ``// Sort all even elements``        ``evens.Sort();``        ``int` `l = 0;``        ` `        ``// Placing even elements in sorted order``        ``for` `(``int` `i = 0; i < n; i++) {``            ``if` `(arr[i] % 2 == 0)``                ``arr[i] = evens[l++];``        ``}`` ` `        ``// Updated array``        ``for` `(``int` `i = 0; i < n; i++)``            ``Console.Write(arr[i] + ``" "``);``    ``}` `    ``// Driver function``    ``public` `static` `void` `Main()``    ``{``        ``int` `N = 5;``        ``int` `[]arr = ``new` `int``[] { 4, 7, 2, 11, 15 };``        ``solve(arr, N);``        ` `    ``}``}` `// This code is contributed by Samim Hossain Mondal`

## Javascript

 ``
Output
`2 7 4 11 15 `

Time Complexity: O(NlogN)
Auxiliary Space: O(N)

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