binarytree.java

JAVA程序设计导论那本书上的一些源代码. 在学那本书的下来的

public class BinaryTree {
  private TreeNode root;

  /** Create a default binary tree */
  public BinaryTree() {
  }

  /** Create a binary tree from an array of objects */
  public BinaryTree(Object[] objects) {
    for (int i = 0; i < objects.length; i++)
      insert(objects[i]);
  }

  /** Insert element o into the binary tree
   * Return true if the element is inserted successfully */
  public boolean insert(Object o) {
    if (root == null)
      root = new TreeNode(o); // Create a new root
    else {
      // Locate the parent node
      TreeNode parent = null;
      TreeNode current = root;
      while (current != null)
        if (((Comparable)o).compareTo(current.element) < 0) {
          parent = current;
          current = current.left;
        }
        else if (((Comparable)o).compareTo(current.element) > 0) {
          parent = current;
          current = current.right;
        }
        else
          return false; // Duplicate node not inserted

      // Create the new node and attach it to the parent node
      if (((Comparable)o).compareTo(parent.element) < 0)
        parent.left = new TreeNode(o);
      else
        parent.right = new TreeNode(o);
    }

    return true; // Element inserted
  }

  /** Inorder traversal */
  public void inorder() {
    inorder(root);
  }

  /** Inorder traversal from a subtree */
  private void inorder(TreeNode root) {
    if (root == null) return;
    inorder(root.left);
    System.out.print(root.element + " ");
    inorder(root.right);
  }

  /** Postorder traversal */
  public void postorder() {
    postorder(root);
  }

  /** Postorder traversal from a subtree */
  private void postorder(TreeNode root) {
    if (root == null) return;
    postorder(root.left);
    postorder(root.right);
    System.out.print(root.element + " ");
  }

  /** Preorder traversal */
  public void preorder() {
    preorder(root);
  }

  /** Preorder traversal from a subtree */
  private void preorder(TreeNode root) {
    if (root == null) return;
    System.out.print(root.element + " ");
    preorder(root.left);
    preorder(root.right);
  }

  /** Inner class tree node */
  private static class TreeNode {
    Object element;
    TreeNode left;
    TreeNode right;

    public TreeNode(Object o) {
      element = o;
    }
  }
}