Given a permutation of first n natural numbers as array and an integer k. Print the lexicographically largest permutation after at most k swaps (https://www.geeksforgeeks.org/largest-permutation-k-swaps/)

kSwapLargestPermutation.java

import java.util.*;
import java.io.*;
import java.lang.*;


public class kSwapLargestPermutation {

	public static void main(String[] args) {
		
		Integer[] numberArray = new Integer[] {4, 5, 2, 1, 3};
		Integer k = 3;
		Integer n = Collections.max(Arrays.asList(numberArray));  // get the maximum element

		Integer[] position = new Integer[n+1];  // create position array with position for elements 0 to n

		for (int x = 0; x < n; x++) {
			position[numberArray[x]] = x;  // fill the position array with position of elements
		}

		for (int i = 0; i < n && k > 0; i++) {

			if (numberArray[i] == n-i) {
				continue;  // if the element in the number array is already the largest then skip forward
			}

			// swap the position of current element and max element
			Integer temp = position[n-i];  // store position of max element
			position[n-i] = position[numberArray[i]];
			position[numberArray[i]] = temp;

			// swap elements in number array using position of max element and position of current element
			Integer tempNumber = numberArray[temp];
			numberArray[temp] = numberArray[i];
			numberArray[i] = tempNumber;

			for (Integer a : numberArray)
				System.out.print(a + " ");
			System.out.println();

			k--;  // decrement k to keep track of swaps

		}

	}

}