Write a program to accept a set of n integers (where n > 0) in a single dimensional array. Arrange the elements of the array such that the lowest number appears in the centre of the array, next lower number in the right cell of the centre, next lower in the left cell of the centre and so on… . The process will stop when the highest number will set in its appropriate cell. Finally, display the array elements.(Pendulum Arrangement of Array)

Assume that the memory space is less. Hence, you don't need to create extra array for the aforesaid task.

Example:

Input: 1 2 3 4 5
Output: 5 3 1 2 4

Input: 11 12 31 14 5
Output: 31 12 5 11 14

import java.util.Scanner;

public class KboatSDAArrange
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter n: ");
        int n = in.nextInt();
        
        if (n <= 0) {
            System.out.println("Invalid Input! n should be greater than 0.");
            return;
        }
        
        int arr[] = new int[n];
        System.out.println("Enter array elements:");
        for (int i = 0; i < n; i++) {
            arr[i] = in.nextInt();
        }
        
        /*
         * Steps to arrange the array:
         * 1. Sort the array
         * {5, 11, 12, 14, 31}
         * 2. Get elements at odd indexes in the array
         * to the right
         * {5, 12, 31, 11, 14}
         * 3. Reverse the sub-array from 0 to (n-1) / 2
         * {31, 12, 5, 11, 14}
         */
        
        //Step 1: Sort the array
        for (int i = 0; i < n - 1; i++) {
            for (int j = 0; j < n - i - 1; j++) {
                if (arr[j] > arr[j + 1]) {
                    int t = arr[j];
                    arr[j] = arr[j+1];
                    arr[j+1] = t;
                }
            } 
        }
        
        //Step 2: Get elements at odd indexes to the right
        int endIdx = n - 1;
        int startIdx;
        
        if (n % 2 == 0) {
            startIdx = n - 1;
        }
        else {
            startIdx = n - 2;
        }
        
        while (startIdx > 0) {
            int t = arr[startIdx];
            int idx = startIdx;
            
            while (idx != endIdx) {
                arr[idx] = arr[idx + 1];
                idx++;
            }
            
            arr[idx] = t;
            startIdx -= 2;
            endIdx -= 1;
        }
        
        //Step 3: Reverse the sub-array from 0 to (n-1) / 2
        for (int i = 0, j = (n - 1) / 2; i < j; i++, j--) {
            int t = arr[i];
            arr[i] = arr[j];
            arr[j] = t;
        }
        
        //Print the final array
        for (int i = 0; i < n; i++) {
            System.out.print(arr[i] + " ");
        }
    }
}