java實現二叉樹

         前幾天有人問我二叉樹的後序非遞歸遍歷怎麼實現，一時沒想起來，今天有時間，就把二叉樹的相關操作都寫了一下，包括創建，中序、先序、後序（遞歸和非遞歸），其中重點的是java在先序創建二叉樹和後序非遞歸遍歷的的實現。

     下面是實現的具體代碼，輸入是工程目錄下input.txt，文件，輸入時“#”表示節點爲空。

package com.algorithm.tree;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Queue;
import java.util.Scanner;
import java.util.Stack;
import java.util.concurrent.LinkedBlockingQueue;


public class Tree<T> {

	private Node<T> root;
	
	public Tree() {
	}
	
	public Tree(Node<T> root) {
		this.root = root;
	}
	
	//創建二叉樹
	public void buildTree() {
		
		Scanner scn = null;
		try {
			scn = new Scanner(new File("input.txt"));
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		root = createTree(root,scn);		
	}
	//先序遍歷創建二叉樹
	private Node<T> createTree(Node<T> node,Scanner scn) {
		
		String temp  = scn.next();
		
		if (temp.trim().equals("#")) {
			return null;
		} else {
			node = new Node<T>((T)temp);
			node.setLeft(createTree(node.getLeft(), scn));
			node.setRight(createTree(node.getRight(), scn));
			return node;
		}
			
	}
	
	
	
	//中序遍歷(遞歸)
	public void inOrderTraverse() {
		inOrderTraverse(root);
	}
	
	public void inOrderTraverse(Node<T> node) {
		if (node != null) {
			inOrderTraverse(node.getLeft());
			System.out.println(node.getValue());
			inOrderTraverse(node.getRight());
		}
	}
	
	
	//中序遍歷(非遞歸)
	public void nrInOrderTraverse() {
		
		Stack<Node<T>> stack = new Stack<Node<T>>();
		Node<T> node = root;
		while (node != null || !stack.isEmpty()) {
			while (node != null) {
				stack.push(node);
				node = node.getLeft();
			}
			node = stack.pop();
			System.out.println(node.getValue());
			node = node.getRight();
			
		}
				
	}
	//先序遍歷(遞歸)
	public void preOrderTraverse() {
		preOrderTraverse(root);
	}
	
	public void preOrderTraverse(Node<T> node) {
		if (node != null) {
			System.out.println(node.getValue());
			preOrderTraverse(node.getLeft());
			preOrderTraverse(node.getRight());
		}
	}
	
	
	//先序遍歷（非遞歸）
	public void nrPreOrderTraverse() {
		
		Stack<Node<T>> stack = new Stack<Node<T>>();
		Node<T> node = root;
		
		while (node != null || !stack.isEmpty()) {
			
			while (node != null) {
				System.out.println(node.getValue());
				stack.push(node);
				node = node.getLeft();
			}
			node = stack.pop();
			node = node.getRight();
		}
				
	}
	
	//後序遍歷(遞歸)
	public void postOrderTraverse() {
		postOrderTraverse(root);
	}
	
	public void postOrderTraverse(Node<T> node) {
		if (node != null) {
			postOrderTraverse(node.getLeft());
			postOrderTraverse(node.getRight());
			System.out.println(node.getValue());
		}
	}
	
	//後續遍歷(非遞歸)
	public void nrPostOrderTraverse() {
		
		Stack<Node<T>> stack = new Stack<Node<T>>();
		Node<T> node = root;
		Node<T> preNode = null;//表示最近一次訪問的節點
		
		while (node != null || !stack.isEmpty()) {
			
			while (node != null) {
				stack.push(node);
				node = node.getLeft();
			}
			
			node = stack.peek();
			
			if (node.getRight() == null || node.getRight() == preNode) {
				System.out.println(node.getValue());
				node = stack.pop();
				preNode = node;
				node = null;
			} else {
				node = node.getRight();
			}
			
		}
		
		
		
		
	}
	
	//按層次遍歷
	public void levelTraverse() {
		levelTraverse(root);
	}
	
	public void levelTraverse(Node<T> node) {
	
		Queue<Node<T>> queue = new LinkedBlockingQueue<Node<T>>();
		queue.add(node);
		while (!queue.isEmpty()) {
			
			Node<T> temp = queue.poll();
			if (temp != null) {
				System.out.println(temp.getValue());
				queue.add(temp.getLeft());
				queue.add(temp.getRight());
			}
						
		}
				
	}
	
	
	
	
}



//樹的節點

class Node<T> {
	
	private Node<T> left;
	private Node<T> right;
	private T value;
	
	public Node() {
	}
	public Node(Node<T> left,Node<T> right,T value) {
		this.left = left;
		this.right = right;
		this.value = value;
	}
	
	public Node(T value) {
		this(null,null,value);
	}
	public Node<T> getLeft() {
		return left;
	}
	public void setLeft(Node<T> left) {
		this.left = left;
	}
	public Node<T> getRight() {
		return right;
	}
	public void setRight(Node<T> right) {
		this.right = right;
	}
	public T getValue() {
		return value;
	}
	public void setValue(T value) {
		this.value = value;
	}
		
}

測試代碼：

package com.algorithm.tree;

public class TreeTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Tree<Integer> tree = new Tree<Integer>();
		tree.buildTree();
		System.out.println("中序遍歷");
		tree.inOrderTraverse();
		tree.nrInOrderTraverse();
		System.out.println("後續遍歷");
		//tree.nrPostOrderTraverse();
		tree.postOrderTraverse();
		tree.nrPostOrderTraverse();
		System.out.println("先序遍歷");
		tree.preOrderTraverse();
		tree.nrPreOrderTraverse();
		
//
	}

}

小弟初次用泛型，不恰當的地方大牛勿噴。