java实现二叉查找树

/**  * @author zyj8170  2011-2-13  *   * 此程序实现一个二叉查找树的功能，可以进行动态插入、删除关键字；  * 查询给定关键字、最小关键字、最大关键字；转换为有序列表(用于排序)  *   *   */import java.util.ArrayList;import java.util.List;public class BinarySearchTree {// 树的根结点private TreeNode root = null;// 遍历结点列表private List<TreeNode> nodelist = new ArrayList<TreeNode>();private class TreeNode {private int key;private TreeNode leftChild;private TreeNode rightChild;private TreeNode parent;public TreeNode(int key, TreeNode leftChild, TreeNode rightChild,TreeNode parent) {this.key = key;this.leftChild = leftChild;this.rightChild = rightChild;this.parent = parent;}public int getKey() {return key;}public String toString() {String leftkey = (leftChild == null ? "" : String.valueOf(leftChild.key));String rightkey = (rightChild == null ? "" : String.valueOf(rightChild.key));return "(" + leftkey + " , " + key + " , " + rightkey + ")";}}/** * isEmpty: 判断二叉查找树是否为空；若为空，返回 true ，否则返回 false . *  */public boolean isEmpty() {if (root == null) {return true;} else {return false;}}/** * TreeEmpty: 对于某些二叉查找树操作(比如删除关键字)来说，若树为空，则抛出异常。 */public void TreeEmpty() throws Exception {if (isEmpty()) {throw new Exception("树为空!");}}/** * search: 在二叉查找树中查询给定关键字 *  * @param key *            给定关键字 * @return 匹配给定关键字的树结点 */public TreeNode search(int key) {TreeNode pNode = root;while (pNode != null && pNode.key != key) {if (key < pNode.key) {pNode = pNode.leftChild;} else {pNode = pNode.rightChild;}}return pNode;}/** * minElemNode: 获取二叉查找树中的最小关键字结点 *  * @return 二叉查找树的最小关键字结点 * @throws Exception *             若树为空，则抛出异常 */public TreeNode minElemNode(TreeNode node) throws Exception {if (node == null) {throw new Exception("树为空！");}TreeNode pNode = node;while (pNode.leftChild != null) {pNode = pNode.leftChild;}return pNode;}/** * maxElemNode: 获取二叉查找树中的最大关键字结点 *  * @return 二叉查找树的最大关键字结点 * @throws Exception *             若树为空，则抛出异常 */public TreeNode maxElemNode(TreeNode node) throws Exception {if (node == null) {throw new Exception("树为空！");}TreeNode pNode = node;while (pNode.rightChild != null) {pNode = pNode.rightChild;}return pNode;}/** * successor: 获取给定结点在中序遍历顺序下的后继结点 *  * @param node *            给定树中的结点 * @return 若该结点存在中序遍历顺序下的后继结点，则返回其后继结点；否则返回 null * @throws Exception */public TreeNode successor(TreeNode node) throws Exception {if (node == null) {return null;}// 若该结点的右子树不为空，则其后继结点就是右子树中的最小关键字结点if (node.rightChild != null) {return minElemNode(node.rightChild);}// 若该结点右子树为空TreeNode parentNode = node.parent;while (parentNode != null && node == parentNode.rightChild) {node = parentNode;parentNode = parentNode.parent;}return parentNode;}/** * precessor: 获取给定结点在中序遍历顺序下的前趋结点 *  * @param node *            给定树中的结点 * @return 若该结点存在中序遍历顺序下的前趋结点，则返回其前趋结点；否则返回 null * @throws Exception */public TreeNode precessor(TreeNode node) throws Exception {if (node == null) {return null;}// 若该结点的左子树不为空，则其前趋结点就是左子树中的最大关键字结点if (node.leftChild != null) {return maxElemNode(node.leftChild);}// 若该结点左子树为空TreeNode parentNode = node.parent;while (parentNode != null && node == parentNode.leftChild) {node = parentNode;parentNode = parentNode.parent;}return parentNode;}/** * insert: 将给定关键字插入到二叉查找树中 *  * @param key *            给定关键字 */public void insert(int key) {TreeNode parentNode = null;TreeNode newNode = new TreeNode(key, null, null, null);TreeNode pNode = root;if (root == null) {root = newNode;return;}while (pNode != null) {parentNode = pNode;if (key < pNode.key) {pNode = pNode.leftChild;} else if (key > pNode.key) {pNode = pNode.rightChild;} else {// 树中已存在匹配给定关键字的结点，则什么都不做直接返回return;}}if (key < parentNode.key) {parentNode.leftChild = newNode;newNode.parent = parentNode;} else {parentNode.rightChild = newNode;newNode.parent = parentNode;}}/** * insert: 从二叉查找树中删除匹配给定关键字相应的树结点 *  * @param key *            给定关键字 */public void delete(int key) throws Exception {TreeNode pNode = search(key);if (pNode == null) {throw new Exception("树中不存在要删除的关键字!");}delete(pNode);}/** * delete: 从二叉查找树中删除给定的结点. *  * @param pNode *            要删除的结点 *  *            前置条件： 给定结点在二叉查找树中已经存在 * @throws Exception */private void delete(TreeNode pNode) throws Exception {if (pNode == null) {return;}if (pNode.leftChild == null && pNode.rightChild == null) { // 该结点既无左孩子结点，也无右孩子结点TreeNode parentNode = pNode.parent;if (pNode == parentNode.leftChild) {parentNode.leftChild = null;} else {parentNode.rightChild = null;}return;}if (pNode.leftChild == null && pNode.rightChild != null) { // 该结点左孩子结点为空，右孩子结点非空TreeNode parentNode = pNode.parent;if (pNode == parentNode.leftChild) {parentNode.leftChild = pNode.rightChild;pNode.rightChild.parent = parentNode;} else {parentNode.rightChild = pNode.rightChild;pNode.rightChild.parent = parentNode;}return;}if (pNode.leftChild != null && pNode.rightChild == null) { // 该结点左孩子结点非空，右孩子结点为空TreeNode parentNode = pNode.parent;if (pNode == parentNode.leftChild) {parentNode.leftChild = pNode.leftChild;pNode.rightChild.parent = parentNode;} else {parentNode.rightChild = pNode.leftChild;pNode.rightChild.parent = parentNode;}return;}// 该结点左右孩子结点均非空，则删除该结点的后继结点，并用该后继结点取代该结点TreeNode successorNode = successor(pNode);delete(successorNode);pNode.key = successorNode.key;}/** * inOrderTraverseList: 获得二叉查找树的中序遍历结点列表 *  * @return 二叉查找树的中序遍历结点列表 */public List<TreeNode> inOrderTraverseList() {if (nodelist != null) {nodelist.clear();}inOrderTraverse(root);return nodelist;}/** * inOrderTraverse: 对给定二叉查找树进行中序遍历 *  * @param root *            给定二叉查找树的根结点 */private void inOrderTraverse(TreeNode root) {if (root != null) {inOrderTraverse(root.leftChild);nodelist.add(root);inOrderTraverse(root.rightChild);}}/** * toStringOfOrderList: 获取二叉查找树中关键字的有序列表 *  * @return 二叉查找树中关键字的有序列表 */public String toStringOfOrderList() {StringBuilder sbBuilder = new StringBuilder(" [ ");for (TreeNode p : inOrderTraverseList()) {sbBuilder.append(p.key);sbBuilder.append(" ");}sbBuilder.append("]");return sbBuilder.toString();}/** * 获取该二叉查找树的字符串表示 */public String toString() {StringBuilder sbBuilder = new StringBuilder(" [ ");for (TreeNode p : inOrderTraverseList()) {sbBuilder.append(p);sbBuilder.append(" ");}sbBuilder.append("]");return sbBuilder.toString();}public TreeNode getRoot() {return root;}public static void testNode(BinarySearchTree bst, TreeNode pNode)throws Exception {System.out.println("本结点: " + pNode);System.out.println("前趋结点: " + bst.precessor(pNode));System.out.println("后继结点: " + bst.successor(pNode));}public static void testTraverse(BinarySearchTree bst) {System.out.println("二叉树遍历：" + bst);System.out.println("二叉查找树转换为有序列表: " + bst.toStringOfOrderList());}public static void main(String[] args) {try {BinarySearchTree bst = new BinarySearchTree();System.out.println("查找树是否为空？ " + (bst.isEmpty() ? "是" : "否"));int[] keys = new int[] { 15, 6, 18, 3, 7, 13, 20, 2, 9, 4 };for (int key : keys) {bst.insert(key);}System.out.println("查找树是否为空？ " + (bst.isEmpty() ? "是" : "否"));TreeNode minkeyNode = bst.minElemNode(bst.getRoot());System.out.println("最小关键字： " + minkeyNode.getKey());testNode(bst, minkeyNode);TreeNode maxKeyNode = bst.maxElemNode(bst.getRoot());System.out.println("最大关键字： " + maxKeyNode.getKey());testNode(bst, maxKeyNode);System.out.println("根结点关键字： " + bst.getRoot().getKey());testNode(bst, bst.getRoot());testTraverse(bst);System.out.println("****************************** ");testTraverse(bst);} catch (Exception e) {System.out.println(e.getMessage());e.printStackTrace();}}}