Sort an array with quick sort - Java Data Structure

Java examples for Data Structure:Sort

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Description

Sort an array with quick sort

Demo Code

public class QuickSortApp
{
  public static void main(String[] args)
  {//  www .ja  v a2 s  .c  o m
    int LEN = 100;
    int[] unsorted = new int[LEN];
    for (int i = 0; i<LEN; i++)
      unsorted[i] = (int)(Math.random() * 100) + 1;
    System.out.println("Unsorted array:");
    printArray(unsorted);
    int[] sorted = sort(unsorted);
    System.out.println("\n\nSorted array:");
    printArray(sorted);
  }

  private static void printArray(int[] array)
  {
    System.out.println();
    for (int i = 0; i < array.length; i++)
    {
      if (array[i] < 10)
        System.out.print(" ");
      System.out.print(array[i] + " ");
      if ((i+1) % 20 == 0)
        System.out.println();
    }
  }

  private static int[] a;

  public static int[] sort(int[] array)
  {
    a = array;
    sort(0, a.length - 1);       // sort the entire array
    return a;
  }

  public static void sort(int low, int high)
  {
    if (low >= high)
      return;
    int p = partition(low, high);
    sort (low, p);
    sort (p+1, high);
  }

  public static int partition(int low, int high)
  {
    int pivot = a[low];

    int i = low - 1;
    int j = high + 1;

    while (i < j)
    {
      for (i++; a[i] < pivot; i++);
      for (j--; a[j] > pivot; j--);
      if (i < j)
        swap(i, j);
    }
    return j;
  }

  public static void swap(int i, int j)
  {
    //int temp = a[i];
    //a[i] = a[j];
    //a[j] = temp;
    a[i] ^= a[j];
    a[j] ^= a[i];
    a[i] ^= a[j];
  }
}

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