【代码示例】

package com.wcs.java; import java.util.ArrayList; import java.util.List; public class BinaryTree { class TreeNode { public String data; //数据 public TreeNode leftNode; //左子树 public TreeNode rightNode; //右子树 public TreeNode(String data, TreeNode leftNode, TreeNode rightNode) { this.data = data; this.leftNode = leftNode; this.rightNode = rightNode; } /** * @return the data */ public String getData() { return data; } /** * @param data the data to set */ public void setData(String data) { this.data = data; } /** * @return the leftNode */ public TreeNode getLeftNode() { return leftNode; } /** * @param leftNode the leftNode to set */ public void setLeftNode(TreeNode leftNode) { this.leftNode = leftNode; } /** * @return the rightNode */ public TreeNode getRightNode() { return rightNode; } /** * @param rightNode the rightNode to set */ public void setRightNode(TreeNode rightNode) { this.rightNode = rightNode; } } public TreeNode init() { TreeNode B = new TreeNode("B", null, null); TreeNode D = new TreeNode("D", null, B); TreeNode C = new TreeNode("C", D, null); TreeNode J = new TreeNode("J", null, null); TreeNode I = new TreeNode("I", J, null); TreeNode G = new TreeNode("G", I, null); TreeNode F = new TreeNode("F", null, G); TreeNode H = new TreeNode("H", null, null); TreeNode E = new TreeNode("E", F, H); TreeNode A = new TreeNode("A", C, E); return A; } private static List<String> list; public String printOut() { StringBuffer stringBuffer = new StringBuffer(); for(int i=0; i<list.size(); i++) { stringBuffer.append(list.get(i) + (i!=list.size()-1 ? "-" : "")); } return stringBuffer.toString(); } public void preorderTraversal(TreeNode node) { //递归先序遍历 if(node != null && node.getData() != null) { list.add(node.getData()); if(node.getLeftNode() != null && node.getLeftNode().getData() != null) { //左子树不为空 preorderTraversal(node.getLeftNode()); } if(node.getRightNode() != null && node.getRightNode().getData() != null) { //右子树不为空 preorderTraversal(node.getRightNode()); } } } public void inorderTraversal(TreeNode node) { //递归中序遍历 if(node != null && node.getData() != null) { if(node.getLeftNode() != null && node.getLeftNode().getData() != null) { inorderTraversal(node.getLeftNode()); } list.add(node.getData()); if(node.getRightNode() != null && node.getRightNode().getData() != null) { inorderTraversal(node.getRightNode()); } } } public void postorderTraversal(TreeNode node) { //递归后序遍历 if(node != null && node.getData() != null) { if(node.getLeftNode() != null && node.getLeftNode().getData() != null) { postorderTraversal(node.getLeftNode()); } if(node.getRightNode() != null && node.getRightNode().getData() != null) { postorderTraversal(node.getRightNode()); } list.add(node.getData()); } } public static void main(String[] args) { //二叉树初始化 BinaryTree binaryTree = new BinaryTree(); TreeNode treeNode = binaryTree.init(); //先序遍历 list = new ArrayList<String>(); binaryTree.preorderTraversal(treeNode); System.out.println("先序遍历: " + binaryTree.printOut()); //中序遍历 list = new ArrayList<String>(); binaryTree.inorderTraversal(treeNode); System.out.println("中序遍历: " + binaryTree.printOut()); //后序遍历 list = new ArrayList<String>(); binaryTree.postorderTraversal(treeNode); System.out.println("后序遍历: " + binaryTree.printOut()); } }

【二叉树】

【运行结果】

先序遍历: A-C-D-B-E-F-G-I-J-H
中序遍历: D-B-C-A-F-J-I-G-E-H
后序遍历: B-D-C-J-I-G-F-H-E-A