Quick Sort In Java

Question

• You are given an array(arr) of integers.
• You have to sort the given array in increasing order using quicksort.

Input Format

An Integer n
arr1
arr2..
n integers

Constraints

1 <= N <= 100000
-10^9 <= arr[i] <= 10^9

Sample Input

5
7
-2
4
1
3

Sample Output

pivot -> 3
Swapping -2 and 7
Swapping 1 and 7
Swapping 3 and 4
pivot index -> 2
pivot -> 1
Swapping -2 and -2
Swapping 1 and 1
pivot index -> 1
pivot -> -2
Swapping -2 and -2
pivot index -> 0
pivot -> 4
Swapping 4 and 7
pivot index -> 3
pivot -> 7
Swapping 7 and 7
pivot index -> 4
-2 1 3 4 7

Program

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

public class Main {

  public static void quickSort(int[] arr, int lo, int hi) {
    //write your code here
    if(lo > hi){
        return;
    }
    
    int pivot = arr[hi];
    int pidex = partition(arr, pivot, lo, hi);
    quickSort(arr, lo, pidex - 1);
    quickSort(arr, pidex + 1, hi);
  }

  public static int partition(int[] arr, int pivot, int lo, int hi) {
    System.out.println("pivot -> " + pivot);
    int i = lo, j = lo;
    while (i <= hi) {
      if (arr[i] <= pivot) {
        swap(arr, i, j);
        i++;
        j++;
      } else {
        i++;
      }
    }
    System.out.println("pivot index -> " + (j - 1));
    return (j - 1);
  }

  // used for swapping ith and jth elements of array
  public static void swap(int[] arr, int i, int j) {
    System.out.println("Swapping " + arr[i] + " and " + arr[j]);
    int temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
  }

  public static void print(int[] arr) {
    for (int i = 0; i < arr.length; i++) {
      System.out.print(arr[i] + " ");
    }
    System.out.println();
  }

  public static void main(String[] args) throws Exception {
    Scanner scn = new Scanner(System.in);
    int n = scn.nextInt();
    int[] arr = new int[n];
    for (int i = 0; i < n; i++) {
      arr[i] = scn.nextInt();
    }
    quickSort(arr, 0, arr.length - 1);
    print(arr);
  }

}