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 <bits/stdc++.h>using namespace std;// Function to arrange array in alternate ordervector<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 codeint 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 approachimport java.util.*;class GFG { // Function to arrange array in alternate order public static ArrayList<Integer> printAlternate(int[] arr, int N) { int i = 0, j = N - 1; ArrayList<Integer> 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<Integer> 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 orderdef 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 codeN = 6arr = [1, 2, 3, 4, 5, 6]# Function callans = printAlternate(arr, N)for x in ans: print(x, end=' ')# This code is contributed by Palak Gupta |
C#
// C# Program to implement the approachusing 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
<script> // JavaScript code for the above approach // Function to arrange array in alternate order function printAlternate(arr, N) { let i = 0, j = N - 1; let ans = []; // Run loop while i <= j while (i <= j) { // Push the element from starting ans.push(arr[i]); // Push the element from back ans.push(arr[j]); // Increment i by 1 i = i + 1; // Decrement j by 1 j = j - 1; } return ans; } // Driver code let N = 6; let arr = [1, 2, 3, 4, 5, 6]; // Function call let ans = printAlternate(arr, N); for (let x of ans) document.write(x + " "); // This code is contributed by Potta Lokesh </script> |
Output
1 6 2 5 3 4
Time Complexity: O(N)
Auxiliary Space: O(N)
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