JAVA中二叉树非递归算法前序，中序，层序遍历

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本文介绍了一种使用Java实现的二叉树构建方法，并提供了前序、中序及层序三种遍历算法的非递归实现。通过具体实例展示了如何初始化一棵二叉树并进行遍历操作。

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一、构造树

package Initialize;
public class TreeNode<T>{

	public T value;
	public TreeNode<T> left;
	public TreeNode<T> right;
	public TreeNode(T val){
		this.value = val;
	}
	public TreeNode(){}
	//输入参数9个节点
	public TreeNode<T> iniTree(T data[]){
		TreeNode<T> node = new TreeNode<T>(data[0]);
		node.left = new TreeNode<T>(data[1]);
		node.right = new TreeNode<T>(data[2]);
		node.left.left = new TreeNode<T>(data[3]);
		node.left.right = new TreeNode<T>(data[4]);
		node.right.left = new TreeNode<T>(data[5]);
		node.right.right = new TreeNode<T>(data[6]);
		node.left.left.left = new TreeNode<T>(data[7]);
		node.left.left.right = new TreeNode<T>(data[8]);
		return node;
	}

}

二、三种遍历算法

package Solutions;

import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;
import Initialize.TreeNode;

public class Solution1 {
	public static void main(String[] args) {
		Integer[] data = {12,11,43,14,89,13,98,65,47};
		TreeNode<Integer> node = new TreeNode<Integer>();
		node = node.iniTree(data);
		System.out.print("前序遍历：");
		new Solution1().PreOrder(node);
		System.out.println();
		System.out.print("中序遍历：");
		new Solution1().InOrder(node);
		System.out.println();
		System.out.print("层序遍历：");
		new Solution1().LevelSort(node);
		
	}
	/*
	 * 非递归方法前序遍历
	 */
	public void PreOrder(TreeNode<Integer> node){
		TreeNode<Integer> p = node;
		Stack<TreeNode<Integer>> stack = new Stack<TreeNode<Integer>>();
		while(p != null || !stack.isEmpty()){
			while(p!=null){
				System.out.print(p.value+" ");
				stack.push(p);
				p = p.left;
			}
			if(!stack.isEmpty()){
				p = stack.pop();
				p = p.right;
			}
		}
	}
	/*
	 * 非递归方法中序遍历
	 */
	public void InOrder(TreeNode<Integer> node){
		TreeNode<Integer> p = node;
		Stack<TreeNode<Integer>> stack = new Stack<TreeNode<Integer>>();
		while(p != null || !stack.isEmpty()){
			while(p!=null){
				stack.push(p);
				p = p.left;
			}
			if(!stack.isEmpty()){
				p = stack.pop();
				System.out.print(p.value+" ");
				p = p.right;
			}
		}
	}
	/*
	 * 非递归方法层序遍历
	 */
	public void LevelSort(TreeNode<Integer> node){
		TreeNode<Integer> p = node;
		Queue<TreeNode<Integer>> queue = new LinkedList<TreeNode<Integer>>();
		queue.add(p);
		while(p != null && !queue.isEmpty()){
			p = queue.remove();
			System.out.print(p.value+" ");
			if(p.left != null){
				queue.add(p.left);
			}
			if(p.right != null){
				queue.add(p.right);
			}
		}
		
	}
	
	

}