# Rearrange given Array by splitting in half and inserting second half in reverse at alternate position

• Difficulty Level : Medium
• Last Updated : 10 Mar, 2022

Given an array arr[] of even length N, the task is to perform the following operations on the given array:

• Split the given array in half.
• Insert the second half in reverse order at alternate positions from the start.

Examples:

Input: N = 6, arr[] = {1, 2, 3, 4, 5, 6}
Output: 1 6 2 5 3 4
Explanation: The first element is 1.
Then print the last element 6
Then the 2nd element 2 followed by the 2nd last element (i.e. the 5th element) 5.
Now print the 3rd element which is 3 and the 3rd last (i.e. the 4th element) 4.

Input: N = 4, arr[] = {12, 34, 11, 20}
Output: 12 20 34 11

Approach: This problem is solved by splitting the array into two parts with the help of two pointers i starting from 0 and j starting from (N-1). Now print the elements at i and j alternatively and increment i/ decrement j when an element at ith / jth position is inserted in new array.

Below is the implementation of the above approach.

## C++

 `// C++ Program to implement the approach``#include ``using` `namespace` `std;` `// Function to arrange array in alternate order``vector<``int``> printAlternate(``int` `arr[], ``int` `N)``{``    ``int` `i = 0, j = N - 1;``    ``vector<``int``> ans;` `    ``// Run loop while i <= j``    ``while` `(i <= j) {` `        ``// Push the element from starting``        ``ans.push_back(arr[i]);` `        ``// Push the element from back``        ``ans.push_back(arr[j]);` `        ``// Increment i by 1``        ``i = i + 1;` `        ``// Decrement j by 1``        ``j = j - 1;``    ``}``    ``return` `ans;``}` `// Driver code``int` `main()``{``    ``int` `N = 6;``    ``int` `arr[N] = { 1, 2, 3, 4, 5, 6 };` `    ``// Function call``    ``vector<``int``> ans = printAlternate(arr, N);``    ``for` `(``int` `x : ans)``        ``cout << x << ``" "``;``    ``return` `0;``}`

## Java

 `// Java Program to implement the approach``import` `java.util.*;` `class` `GFG {` `  ``// Function to arrange array in alternate order``  ``public` `static` `ArrayList``    ``printAlternate(``int``[] arr, ``int` `N)``  ``{``    ``int` `i = ``0``, j = N - ``1``;``    ``ArrayList ans = ``new` `ArrayList<>();` `    ``// Run loop while i <= j``    ``while` `(i <= j) {` `      ``// Push the element from starting``      ``ans.add(arr[i]);` `      ``// Push the element from back``      ``ans.add(arr[j]);` `      ``// Increment i by 1``      ``i = i + ``1``;` `      ``// Decrement j by 1``      ``j = j - ``1``;``    ``}``    ``return` `ans;``  ``}` `  ``public` `static` `void` `main(String[] args)``  ``{``    ``int` `N = ``6``;``    ``int` `arr[] = { ``1``, ``2``, ``3``, ``4``, ``5``, ``6` `};` `    ``// Function call``    ``ArrayList ans = printAlternate(arr, N);``    ``for` `(``int` `x : ans)``      ``System.out.print(x + ``" "``);``  ``}``}` `// This code is contributed by ninja_hattori.`

## Python3

 `# Python Program to implement the approach``# Function to arrange array in alternate order` `def` `printAlternate(arr, N):``    ``i ``=` `0``    ``j ``=` `N ``-` `1``    ``ans ``=` `[]` `    ``# Run loop while i <= j``    ``while` `(i <``=` `j):` `        ``# Push the element from starting``        ``ans.append(arr[i])` `        ``# Push the element from back``        ``ans.append(arr[j])` `        ``# Increment i by 1``        ``i ``=` `i ``+` `1` `        ``# Decrement j by 1``        ``j ``=` `j ``-` `1` `    ``return` `ans`  `# Driver code` `N ``=` `6``arr ``=` `[``1``, ``2``, ``3``, ``4``, ``5``, ``6``]` `# Function call``ans ``=` `printAlternate(arr, N)``for` `x ``in` `ans:``    ``print``(x, end``=``' '``)` `# This code is contributed by Palak Gupta`

## C#

 `// C# Program to implement the approach``using` `System;``using` `System.Collections;` `class` `GFG {` `  ``// Function to arrange array in alternate order``  ``static` `ArrayList printAlternate(``int``[] arr, ``int` `N)``  ``{``    ``int` `i = 0, j = N - 1;``    ``ArrayList ans = ``new` `ArrayList();` `    ``// Run loop while i <= j``    ``while` `(i <= j) {` `      ``// Push the element from starting``      ``ans.Add(arr[i]);` `      ``// Push the element from back``      ``ans.Add(arr[j]);` `      ``// Increment i by 1``      ``i = i + 1;` `      ``// Decrement j by 1``      ``j = j - 1;``    ``}``    ``return` `ans;``  ``}` `  ``// Driver code``  ``public` `static` `void` `Main()``  ``{``    ``int` `N = 6;``    ``int``[] arr = { 1, 2, 3, 4, 5, 6 };` `    ``// Function call``    ``ArrayList ans = printAlternate(arr, N);``    ``foreach``(``int` `x ``in` `ans) Console.Write(x + ``" "``);``  ``}``}` `// This code is contributed by Samim Hossain Mondal.`

## Javascript

 ``

Output

`1 6 2 5 3 4 `

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

My Personal Notes arrow_drop_up