二叉树的递归和非递归遍历（java）

package com.wy.binarytree;import java.util.ArrayList;import java.util.LinkedList;import java.util.Queue;import java.util.Stack;import com.wy.binarytree.BinaryTree.TreeNode;public class BinaryTree {private TreeNode root = null;public BinaryTree() {root = new TreeNode(1, "A");}/** * 构建二叉树 A B C D E F */public void createBinaryTree() {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");root.leftChild = nodeB;root.rightChild = nodeC;nodeB.leftChild = nodeD;nodeB.rightChild = nodeE;nodeC.rightChild = nodeF;}/** * 求二叉树的高度 * */public int getHeight() {return getHeight(root);}private int getHeight(TreeNode node) {if (node == null) {return 0;} else {int i = getHeight(node.leftChild);int j = getHeight(node.rightChild);return (i < j) ? j + 1 : i + 1;}}/** * 获取二叉树的结点数 * */public int getSize() {return getSize(root);}private int getSize(TreeNode node) {if (node == null) {return 0;} else {return 1 + getSize(node.leftChild) + getSize(node.rightChild);}}/** * 前序遍历——迭代 * */public void preOrder(TreeNode node) {if (node == null) {return;} else {System.out.print(node.getData());preOrder(node.leftChild);preOrder(node.rightChild);}}/** * 中序遍历——迭代 * */public void midOrder(TreeNode node) {if (node == null) {return;} else {midOrder(node.leftChild);System.out.print(node.getData());midOrder(node.rightChild);}}/** * 后序遍历——迭代 *  * @author Administrator * */public void postOrder(TreeNode node) {if (node == null) {return;} else {postOrder(node.leftChild);postOrder(node.rightChild);System.out.print(node.getData());}}/** * 前序遍历——非迭代 */public void nonRecOrder(TreeNode node) {if (node == null) {return;}Stack<TreeNode> stack = new Stack<TreeNode>();stack.push(node);while (!stack.isEmpty()) {TreeNode n = stack.pop();// 弹出根结点System.out.print(n.getData());if (n.rightChild != null) {stack.push(n.rightChild);}if (n.leftChild != null) {stack.push(n.leftChild);}}}/** * 非递归前序遍历 */public void nonRecursivePreOrder(TreeNode node) {Stack<TreeNode> stack = new Stack<TreeNode>();TreeNode current;current = node;while ((current != null) || (!stack.isEmpty())) {if (current != null) {System.out.print(current.data);stack.push(current);current = current.leftChild;} else {current = (TreeNode) stack.peek();stack.pop();current = current.rightChild;}}}/** * 非递归中序遍历 */public void nonRecursiveMidOrder(TreeNode node) {Stack<TreeNode> stack = new Stack<TreeNode>();TreeNode current;current = node;while ((current != null) || (!stack.empty())) {if (current != null) {stack.push(current);current = current.leftChild;} else {current = (TreeNode) stack.pop();;System.out.print(current.data);current = current.rightChild;}}}/** * 非递归后序遍历 */public void nonRecursivePostOrder(TreeNode node) {Stack<TreeNode> s = new Stack<TreeNode>();Stack<Integer> s2 = new Stack<Integer>();Integer i = new Integer(1);while (node != null || !s.empty()) {while (node != null) {s.push(node);s2.push(new Integer(0));node = node.leftChild;}while (!s.empty() && s2.peek().equals(i)) {s2.pop();System.out.print(s.pop().data);}if (!s.empty()) {s2.pop();s2.push(new Integer(1));node = s.peek();node = node.rightChild;}}}/** * 树的层次遍历 */public void bfs(TreeNode node) {Queue<TreeNode> queue = new LinkedList<TreeNode>();TreeNode current;current = node;while ((current != null) || (!queue.isEmpty())) {if (current != null) {System.out.print(current.data);queue.add(current.leftChild);queue.add(current.rightChild);current = queue.poll();} else {current = queue.poll();}}}public class TreeNode {private int index;private String data;private TreeNode leftChild;private TreeNode rightChild;public int getIndex() {return index;}public void setIndex(int index) {this.index = index;}public String getData() {return data;}public void setData(String data) {this.data = data;}public TreeNode(int index, String data) {this.index = index;this.data = data;this.leftChild = null;this.rightChild = null;}}public static void main(String[] args) {BinaryTree binaryTree = new BinaryTree(); binaryTree.createBinaryTree(); int height = binaryTree.getHeight(); System.out.println("treeHeihgt:"+height); int size = binaryTree.getSize(); System.out.println("treeSize:"+size); System.out.println(); System.out.print("前序-递归："); binaryTree.preOrder(binaryTree.root); System.out.println(); System.out.print("中序-递归："); binaryTree.midOrder(binaryTree.root); System.out.println(); System.out.print("后序-递归："); binaryTree.postOrder(binaryTree.root); System.out.println(); System.out.print("前序-非递归："); binaryTree.nonRecursivePreOrder(binaryTree.root); System.out.println(); System.out.print("中序-非递归："); binaryTree.nonRecursiveMidOrder(binaryTree.root); System.out.println(); System.out.print("后序-非递归："); binaryTree.nonRecursivePostOrder(binaryTree.root); System.out.println(); System.out.print("树的层次遍历："); binaryTree.bfs(binaryTree.root);// 前序生成二叉树；String[] data = new String[] { "A", "B","D", "#","#",  "E", "#", "#", "C", "#","F","#","#"};ArrayList<String> arrayList = new ArrayList<>();for (String s : data) {arrayList.add(s);}TreeNode tree = binaryTree.createBinaryTreePre(arrayList);System.out.print("前序生成二叉树：");binaryTree.preOrder(tree);}/** * 通过前序遍历的数据反向生成二叉树 *  * @param arrayList */private TreeNode createBinaryTreePre(ArrayList<String> data) {return createBinaryTree(data.size(), data);}private TreeNode createBinaryTree(int size, ArrayList<String> data) {if (data.size() == 0)return null;String d = data.get(0);int index = size-data.size();if (d.equals("#")) {data.remove(0);return null;}TreeNode node = new TreeNode(index, d);if (index == 0) {root = node;}data.remove(0);node.leftChild = createBinaryTree(size, data);node.rightChild = createBinaryTree(size, data);return node;}}输出：treeHeihgt:3treeSize:6前序-递归：ABDECF中序-递归：DBEACF后序-递归：DEBFCA前序-非递归：ABDECF中序-非递归：DBEACF后序-非递归：DEBFCA树的层次遍历：ABCDEF前序生成二叉树：ABDECF