QuickSort.java

import java.io.*;
  
class QuickSort {
      
// A utility function to swap two elements
static void swap(int[] arr, int i, int j)
{
    int temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
}
  
/* This function takes last element as pivot, places
   the pivot element at its correct position in sorted
   array, and places all smaller (smaller than pivot)
   to left of pivot and all greater elements to right
   of pivot */
static int partition(int[] arr, int low, int high)
{
      
    // pivot
    int pivot = arr[high]; 
      
    // Index of smaller element and
    // indicates the right position
    // of pivot found so far
    int i = (low - 1); 
  
    for(int j = low; j <= high - 1; j++)
    {
          
        // If current element is smaller 
        // than the pivot
        if (arr[j] < pivot) 
        {
              
            // Increment index of 
            // smaller element
            i++; 
            swap(arr, i, j);
        }
    }
    swap(arr, i + 1, high);
    return (i + 1);
}
  
/* The main function that implements QuickSort
          arr[] --> Array to be sorted,
          low --> Starting index,
          high --> Ending index
 */
static void quickSort(int[] arr, int low, int high)
{
    if (low < high) 
    {
          
        // pi is partitioning index, arr[p]
        // is now at right place 
        int pi = partition(arr, low, high);
  
        // Separately sort elements before
        // partition and after partition
        quickSort(arr, low, pi - 1);
        quickSort(arr, pi + 1, high);
    }
}
  
// Function to print an array 
static void printArray(int[] arr, int size)
{
    for(int i = 0; i < size; i++)
        System.out.print(arr[i] + " ");
          
    System.out.println();
}
  
// Driver Code
public static void main(String[] args)
{
    int[] arr = { 10, 7, 8, 9, 1, 5 };
    int n = arr.length;
      
    quickSort(arr, 0, n - 1);
    System.out.println("Sorted array: ");
    printArray(arr, n);
}
}