java實現二叉樹的建立以及前序中序後序遍歷

可以結合這篇文章：http://blog.csdn.net/u014285517/article/details/50440829

代碼如下：

package com.company;

import java.io.IOException;

public class Test5 {

    public static class TreeNode {
        char val;
        TreeNode left;
        TreeNode right;
        TreeNode(char val) {
            this.val = val;
        }
    }

    static TreeNode createBinaryTree() {
        char ch = 0;
        try {//java讀入單個字符
            ch = (char)System.in.read();
        } catch (IOException e) {
            e.printStackTrace();
        }
        if (ch == '#') {
            return null;
        } else {
            TreeNode treeNode = new TreeNode(ch);
            treeNode.left = createBinaryTree();
            treeNode.right = createBinaryTree();
            return treeNode;
        }
    }

    static void frontTraverse(TreeNode treeNode) {
        if (treeNode == null) {
            return;
        }
        System.out.print(treeNode.val);
        frontTraverse(treeNode.left);
        frontTraverse(treeNode.right);
    }

    static void middleTraverse(TreeNode treeNode) {
        if (treeNode == null) {
            return;
        }
        middleTraverse(treeNode.left);
        System.out.print(treeNode.val);
        middleTraverse(treeNode.right);
    }

    static void endTraverse(TreeNode treeNode) {
        if (treeNode == null) {
            return;
        }
        endTraverse(treeNode.left);
        endTraverse(treeNode.right);
        System.out.print(treeNode.val);
    }

    public static void main(String[] args)  {
        TreeNode root = createBinaryTree();
        frontTraverse(root);
        System.out.println();
        middleTraverse(root);
        System.out.println();
        endTraverse(root);
    }

}