数据结构之二叉树的Java实现

来源：互联网发布：2016中国经济数据公布编辑：程序博客网时间：2024/05/14 15:45
Java代码如下：
package com.ds.tree;import com.ds.list.MyStack;/** * 二叉树 */public class BinaryTree {    private static int index = 0;    static class Node {        public char data;        public Node left;        public Node right;        public boolean isVisited = false; //是否被访问了，在后序非递归算法中用到    }    private Node root;    //先序创建二叉树，数据域为'#'表示空节点    public BinaryTree create(char[] data) {        if(data == null || data.length == 0) {            return null;        }        index = 0;        root = createBinaryTree(data);        return this;    }    //先序创建二叉树的递归算法    private Node createBinaryTree(char[] data) {        char c = data[index++];        Node node = new Node();        if(c == '#') {            node.data = '#';            node.left = null;            node.right = null;        }else {            node.data = c;            node.left = createBinaryTree(data);            node.right = createBinaryTree(data);        }        return node;    }    //获取根节点    public Node getRoot() {        return this.root;    }    //先序遍历    public void preOrder() {        preorder(root);        System.out.println();    }    //先序遍历递归算法    private void preorder(Node node) {        if(!isEmptyNode(node)) {            visit(node);            preorder(node.left);            preorder(node.right);        }    }    //先序遍历非递归算法    public void _preOrder() {        MyStack<Node> stack = new MyStack<>();        Node p = this.root;        while(!isEmptyNode(p) || !stack.isEmpty()) {            if(!isEmptyNode(p)) { //判断节点是否为空                visit(p);                stack.push(p);                p = p.left;            }else {                p = stack.pop();                p = p.right;            }        }        System.out.println();    }    //中序遍历    public void inOrder() {        inorder(root);        System.out.println();    }    //中序遍历递归算法    private void inorder(Node node) {        if(!isEmptyNode(node)) {            inorder(node.left);            visit(node);            inorder(node.right);        }    }    //中序遍历非递归算法    public void _inOrder() {        MyStack<Node> stack = new MyStack<>();        Node p = this.root;        while(!isEmptyNode(p) || !stack.isEmpty()) {            if(!isEmptyNode(p)) {                stack.push(p);                p = p.left;            }else {                p = stack.pop();                visit(p);                p = p.right;            }        }        System.out.println();    }    //后序遍历    public void postOrder() {        postorder(root);        System.out.println();    }    //后序遍历递归算法    private void postorder(Node node) {        if(!isEmptyNode(node)) {            postorder(node.left);            postorder(node.right);            visit(node);        }    }    //后序遍历非递归算法    public void _postOrder() {        MyStack<Node> stack = new MyStack<>();        Node p = this.root;        while(!isEmptyNode(p) || !stack.isEmpty()) {            if(!isEmptyNode(p)) {                stack.push(p);                p = p.left;            }else {                p = stack.peek();                //判断p的左右孩子节点是否都被访问过，如果都被访问过，则访问p节点                if(isChildrenVisited(p)) {                    visit(p);                    p.isVisited = true;                    stack.pop();                    p = null;                }else {                    p = p.right;                }            }        }        System.out.println();    }    //判断一个节点是否为空节点    private boolean isEmptyNode(Node node) {        return node == null || (node != null && node.data == '#');    }    //判断一个节点的两个孩子节点是否都被访问了    private boolean isChildrenVisited(Node node) {        if(isEmptyNode(node.left) && isEmptyNode(node.right)) {            //空节点默认是被访问过的            return true;        }        return node.left.isVisited && node.right.isVisited;    }    //访问节点，打印节点数据域    private void visit(Node node) {        System.out.print(node.data + " ");    }    public static void main(String[] args) {        String s = "-+a##*b##-c##d##/e##f##";        char[] data = s.toCharArray();        BinaryTree tree = new BinaryTree().create(data);        System.out.println("pre order result: ");        tree.preOrder();        System.out.println("_pre order result: ");        tree._preOrder();        System.out.println("in order result: ");        tree.inOrder();        System.out.println("_in order result: ");        tree._inOrder();        System.out.println("post order result: ");        tree.postOrder();        System.out.println("_post order result: ");        tree._postOrder();    }}
MyStack为自定义的栈结构，参见：http://blog.csdn.net/yubo_725/article/details/52195459
代码运行结果如下：
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