QuickSort.java

public class QuickSort {
    public static void quickSort(int[] arr, int low, int high) {
        if (low < high) {
            int pivotIndex = partition(arr, low, high);
            
            quickSort(arr, low, pivotIndex - 1); // Sort the left subarray
            quickSort(arr, pivotIndex + 1, high); // Sort the right subarray
        }
    }

    public static int partition(int[] arr, int low, int high) {
        int pivot = arr[high]; // Choose the pivot as the last element
        int i = low - 1; // Index of the smaller element
        
        for (int j = low; j < high; j++) {
            if (arr[j] <= pivot) {
                i++;
                // Swap arr[i] and arr[j]
                int temp = arr[i];
                arr[i] = arr[j];
                arr[j] = temp;
            }
        }
        
        // Swap arr[i+1] and arr[high] (pivot)
        int temp = arr[i + 1];
        arr[i + 1] = arr[high];
        arr[high] = temp;

        return i + 1;
    }

    public static void main(String[] args) {
        int[] arr = {15, 12, 19, 13, 16};
        int n = arr.length;
        
        System.out.println("Original array:");
        for (int num : arr) {
            System.out.print(num + " ");
        }
        System.out.println();
        
        quickSort(arr, 0, n - 1);
        
        System.out.println("Sorted array:");
        for (int num : arr) {
            System.out.print(num + " ");
        }
    }
}