Lectures Notes on 24 October 2011

public class Permute
{
  public static void printArray (int[] a)
  {
    for (int i = 0; i < a.length; i++)
    {
      System.out.print (a[i] + "  ");
    }
    System.out.println ();
  }

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

  public static void permute (int[] a, int lo, int hi)
  {
    if (lo == hi)
    {
      printArray (a);
    }
    else
    {
     for (int i = lo; i <= hi; i++)
     {
       swap (a, lo, i);
       permute (a, lo + 1, hi);
       swap (a, i, lo);
     }
    }
  }

  public static void main (String[] args)
  {
    int[] a = {1, 2, 3, 4};
    permute (a, 0, a.length - 1);
  }
}