ТЕМА 14

import java.util.Arrays;
import java.util.Scanner;

public class QuickSort {
    public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
        System.out.println("Enter number of elements: ");
    int N = scan.nextInt();
    int[] arr = new int[N];
        for (int i = 0; i < N; i++) {
        System.out.print("Enter element " + i + " :");
        arr[i] = Integer.parseInt(scan.next());
    }
    //print before//
        System.out.println("BEFORE SORT: " + Arrays.toString(arr));

    quickSort(arr, 0, N -1);

    //print after//
        System.out.println("AFTER SORT: " + Arrays.toString(arr));
    }//end of main//


    public static void quickSort(int[] arr, int low, int high){
        if(low < high){
            int pi = partition(arr, low, high);
            quickSort(arr, low, pi - 1);
            quickSort(arr, pi + 1, high);
        }
    }//end of quickSort//

    public static int partition(int[] arr, int low, int high){
        int pivot = arr[high];
        int i = low - 1;
        for (int j = low; j < high; j++) {
            if(arr[j] < pivot){
                i++;
                //swap//
                int temp = arr[j];
                arr[j] = arr[i];
                arr[i] = temp;
            }
        }
        //put  the pivot element at the right position//
        int temp = arr[high];
        arr[high] = arr[i + 1];
        arr[i + 1] = temp;
        return i + 1;
    }//end of partition//
}//end of class//