// Source code example for "A Practical Introduction
// to Data Structures and Algorithm Analysis"
// by Clifford A. Shaffer, Prentice Hall, 1998.
// Copyright 1998 by Clifford A. Shaffer

class GenTree {   // General Tree class for UNION/FIND
  private GTNode[] array;               // Node array

  public GenTree(int size) {            // Constructor
    array = new GTNode[size];           // Create node array
    for (int i=0; i<size; i++)
      array[i] = new GTNode();
  }

  public boolean differ(int a, int b) { // Nodes in different trees?
    GTNode root1 = FIND(array[a]);      // Find root of node a
    GTNode root2 = FIND(array[b]);      // Find root of node b
    return root1 != root2;              // Compare roots
  }

  public void UNION(int a, int b) {     // Merge two subtrees
    GTNode root1 = FIND(array[a]);      // Find root of node a
    GTNode root2 = FIND(array[b]);      // Find root of node b
    if (root1 != root2) root2.setParent(root1); // Merge subtrees
  }

  private GTNode FIND(GTNode curr) {    // Find root
    while (curr.parent() != null) curr = curr.parent();
    return curr;                        // At root
  }

  void print() { // Print out the contents of the array
    for (int i=0; i<array.length; i++) {
      GTNode temp = array[i].parent();
      if (temp == null)	System.out.print("-1 "); // root
      else // Find which array index holds this object.
	    // In other words, map the logical tree node to its array index.
        // This is expensive, but this printing step is artificial --
		// it is not needed to do the actual equivalence processing.
        for (int j=0; j<array.length; j++) 
          if (temp == array[j]) {
            System.out.print(" " + j + " ");
            break;
          }
    }
    System.out.println();
  }
}