Quick sort on array of int - Java Data Structure

Java examples for Data Structure:Sort

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Description

Quick sort on array of int

Demo Code

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class Main {
  public static void main(String ags[]) {
    int a[] = new int[10];
    for (int i = 0; i < a.length; i++) {
      a[i] = new Random().nextInt(10);
    }/*  w ww.j av  a 2  s.  c  o m*/
    quicksort(a, 0, a.length - 1);

  }

  static int patition(int[] a, int start, int end) {
    int pivot = a[start];
    List s = new ArrayList();
    List l = new ArrayList();

    for (int j = start + 1; j <= end; j++) {
      if (a[j] <= pivot) {
        s.add(a[j]);
      } else {
        l.add(a[j]);
      }
    }

    for (int j = 0; j < s.size(); j++) {
      a[start + j] = (Integer) s.toArray()[j];
    }

    a[start + s.size()] = pivot;
    for (int j = 0; j < l.size(); j++) {
      a[s.size() + start + j + 1] = (Integer) l.toArray()[j];
    }

    return start + s.size();
  }

  static void quicksort(int[] a, int start, int end) {
    if (start < end) {
      int q = patition(a, start, end);
      quicksort(a, start, q - 1);
      quicksort(a, q + 1, end);
      printa(a, start, end);
    }
  }

  static void printa(int[] a, int stat, int end) {
    for (int i = stat; i <= end; i++) {
      System.out.print(a[i] + " ");
    }
    System.out.println("");
  }
}

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