二叉树遍历的递归与非递归实现（java）

package com.Tree;import java.util.Stack;public class BinaryTree {//定义每棵树的根节点private TreeNode root = null;//二叉树类的构造函数，即为创建根节点public BinaryTree(){root = new TreeNode(1, "root(A)");}/* * 创建一棵根节点为A的二叉树 * A * B C * D E F * G H I *///建立一个如上图的二叉树public void buildBinTree(TreeNode root) {TreeNode nodeB= new TreeNode(2, "B");TreeNode nodeC= new TreeNode(3, "C");TreeNode nodeD= new TreeNode(4, "D");TreeNode nodeE= new TreeNode(5, "E");TreeNode nodeF= new TreeNode(6, "F");TreeNode nodeG= new TreeNode(7, "G");TreeNode nodeH= new TreeNode(8, "H");TreeNode nodeI= new TreeNode(9, "I");root.leftChild=nodeB;root.rightChild=nodeC;nodeB.leftChild=nodeD;nodeB.rightChild=nodeE;nodeC.rightChild=nodeF;nodeE.leftChild=nodeG;nodeE.rightChild=nodeH;nodeF.leftChild=nodeI;}//检查二叉树是否为空public boolean isEmpty(){return root==null;}//树的高度public int TreeHeight() {return height(root);}private int height(TreeNode root) {if (root==null) {return 0;}else{int i=height(root.leftChild);int j=height(root.rightChild);return (i<j)?(j+1):(i+1);}}//节点的个数public int TreeSize(){return size(root);}private int size(TreeNode root) {if (root==null) {return 0;}else {return 1+size(root.leftChild)+size(root.rightChild);}}//二叉树的递归前序遍历（根左右）public void preTraversal(TreeNode root) {if (root!=null) {visit(root);preTraversal(root.leftChild);preTraversal(root.rightChild);}}//二叉树前序遍历的非递归实现public void preOrder(TreeNode root){Stack TreeStack = new Stack<>();if (root!=null) {TreeStack.push(root);while(!TreeStack.isEmpty()){root = TreeStack.pop();visit(root);if (root.rightChild!=null) {TreeStack.push(root.rightChild);}if (root.leftChild!=null){TreeStack.push(root.leftChild);}}}}//二叉树的中序遍历（左根右）public void inTraversal(TreeNode root){if (root!=null) {inTraversal(root.leftChild);visit(root);inTraversal(root.rightChild);}}//二叉树中序遍历的非递归实现public void inorder(TreeNode root){Stack TreeStack = new Stack<>();while(root!=null) {//中序遍历依次将右子节点、根节点入栈，然后将左子节点赋予根节点，//直到找出首先出栈的左子节点while(root!=null){if (root.rightChild!=null) TreeStack.push(root.rightChild);TreeStack.push(root);root=root.leftChild;}//获取栈顶元素root = TreeStack.pop();//将没有右子节点的全部出栈while(!TreeStack.empty()&&root.rightChild==null){visit(root);root=TreeStack.pop();}//若有右子节点，则首先输出根节点visit(root);//若根节点有右子节点，则依次出栈获取跟节点的右子节点if (!TreeStack.empty()) {root=TreeStack.pop();}else {root=null;}}}//二叉树的后续遍历（左右根）public void postTraversal(TreeNode root){if (root!=null) {postTraversal(root.leftChild);postTraversal(root.rightChild);visit(root);}}//二叉树后序遍历的非递归实现public void postorder(TreeNode root){//用来记录某节点的右子节点是否已经输出TreeNode temp = root;Stack TreeStack = new Stack<>();while(root!=null){//左子树入栈for(;root.leftChild!=null;root=root.leftChild){TreeStack.push(root);}//当前节点无右子节点或右子节点已经输出while(root!=null&&(root.rightChild==null||root.rightChild==temp)){visit(root);//记录刚输出的节点temp=root;if (TreeStack.empty()) {return;}root = TreeStack.pop();}//处理右子节点TreeStack.push(root);root=root.rightChild;}}//访问一个节点的函数public void visit(TreeNode visitNode) {visitNode.isVisited=true;System.out.println("--name:"+visitNode.data);}private class TreeNode{private int key = 0;private String data = null;private boolean isVisited = false;private TreeNode leftChild = null;private TreeNode rightChild = null;//无参的构造函数public TreeNode(){}//有参的构造函数public TreeNode(int key,String data){this.key=key;this.data=data;}}public static void main(String[] args) {BinaryTree bTree = new BinaryTree();bTree.buildBinTree(bTree.root);System.out.println("该树的节点数:"+bTree.size(bTree.root));System.out.println("该树的深度为："+bTree.height(bTree.root));System.out.println("递归实现前序遍历:");bTree.preTraversal(bTree.root);System.out.println("非递归实现前序遍历:");bTree.preOrder(bTree.root);System.out.println("递归实现中序遍历:");bTree.inTraversal(bTree.root);System.out.println("非递归实现中序遍历：");bTree.inorder(bTree.root);System.out.println("递归实现后序遍历:");bTree.postTraversal(bTree.root);System.out.println("非递归实现后序遍历：");bTree.postorder(bTree.root);}}</treenode></treenode></treenode>