二叉树的各种非递归遍历

二叉树的结构：

package com.ydp.tree.btree;
public class BTreeNode {
		public BTreeNode rchild = null;
		public BTreeNode lchild = null;
		public int	data;
		
		public boolean isFirst = true;//后序遍历使用，是否是首次入栈
		
		public BTreeNode(){}
		public BTreeNode(int data){
			this.data=data;
		}
	}

二叉树的各种遍历：

package com.ydp.tree.btree;

import java.util.ArrayList;
import java.util.List;
import java.util.Queue;
import java.util.Stack;
import java.util.concurrent.ArrayBlockingQueue;

public class BTree {

	public static void main(String[] args) {
		BTree tree = new BTree();
		BTreeNode  root = new BTreeNode();	
		ArrayList<Integer> list = new ArrayList<Integer>();
		for(int i=1;i<=10;i++){
			list.add(i);
		}
		tree.createTree(root,list);
		System.out.println("层次遍历：");
		tree.levelOrder(root);
		System.out.println("\n先序遍历：");
		tree.preOrder(root);
		System.out.println("\n中序遍历：");
		tree.midOrder(root);
		System.out.println("\n后序遍历：");
		tree.postOrder(root);
	}	
	
	//创建二叉树
	 void createTree(BTreeNode root,List<Integer> list){	
		 BTreeNode  node = root;
		 root.data=list.get(0);
		 int index = 1;
		 Queue<BTreeNode>  queue = new ArrayBlockingQueue<BTreeNode>(100);		 
		 while(index < list.size() && node != null){
			 node.lchild=new BTreeNode(list.get(index));
			 queue.add(node.lchild);
			 if(++index < list.size()){
				 node.rchild=new BTreeNode(list.get(index));
				 queue.add(node.rchild);
			 }
			 index++;
			 node = queue.poll();
		 }	
	 }
	//层次遍历
	 void levelOrder(BTreeNode root){
		 Queue<BTreeNode>  queue = new ArrayBlockingQueue<BTreeNode>(100);
		 queue.add(root);
		 BTreeNode node = null;
		 while(queue.size()>0){
			 node = queue.poll();
			 System.out.print(node.data+" ");
			 if(node.lchild != null){
				 queue.add(node.lchild);
			 }
			 if(node.rchild != null){
				 queue.add(node.rchild);
			 }
		 }		 
	 }
	 
	 //先序遍历
	 void preOrder(BTreeNode root){
		 Stack<BTreeNode> stack = new Stack<BTreeNode>();
		 BTreeNode node = root;			 
		 while(node != null || !stack.empty()){
			 while(node != null){
				 System.out.print(node.data+" ");
				 stack.push(node);
				 node = node.lchild;
			 }			 
			 node = stack.pop();			
			 node =  node.rchild;
		 }	
	 }
	 
	 //中序遍历
	 void midOrder(BTreeNode root){
		 Stack<BTreeNode> stack = new Stack<BTreeNode>();
		 BTreeNode node = root;
				 
		 while(node != null || !stack.empty()){
			 while(node != null){
				 stack.push(node);
				 node = node.lchild;
			 }			 
			 node = stack.pop();
			 System.out.print(node.data+" ");
			 node =  node.rchild;
		 }		
	 }
	 
	//后序遍历
	 void postOrder(BTreeNode root){
		 Stack<BTreeNode> stack = new Stack<BTreeNode>();
		 BTreeNode node = root;
		 
		 while(node != null || !stack.empty() ){
			 while(node != null && node.isFirst != false){
				 stack.push(node);
				 node = node.lchild;
			 }
			 node = stack.pop();
			 if(node.isFirst == false || node.rchild == null ){
				 System.out.print(node.data +" ");
				 node = null;
			 }else{
				 node.isFirst =  false;
				 stack.push(node);
				 node = node.rchild;
			 }
		 }
	 }
	
}