二叉树的遍历（Java，前序、中序、后序、递归and非递归）

 

package com.cuitccol.claymore;

import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;
import java.util.ArrayList;
import java.util.Map;

public class BTree {
    
    private BinaryTreeNode root;
    /**
     * 前序递归
     * @param current
     */
    public void PreOrder(BinaryTreeNode current){
        if(current!=null){
            System.out.println(current.getInfo());
            PreOrder(current.lchild);
            PreOrder(current.rchild);
        }
    }
    /**
     * 中序递归
     * @param current
     */
    public void inOrder(BinaryTreeNode current){
        if(current!=null){
            inOrder(current.lchild);
            System.out.println(current.getInfo());
            inOrder(current.rchild);
        }
    }
    /**
     * 后序递归
     * @param current
     */
    public void postOrder(BinaryTreeNode current){
        if(current!=null){
            postOrder(current.lchild);
            postOrder(current.rchild);
            System.out.println(current.getInfo());
        }
    }
    /**
     * 深度递归
     * @param current
     * @return deep
     */
    public int deepth(BinaryTreeNode current){
        if(current == null){
            return 0;
        }else{
            int dep1 = deepth(current.lchild);
            int dep2 = deepth(current.rchild);
            return dep1>dep2?dep1+1:dep2+1;
        }
    }
    
    /**
     * 前序非递归
     * @param current
     */
    public void preOrderNonRecursive(BinaryTreeNode current){
        Stack<BinaryTreeNode> stack = new Stack<BTree.BinaryTreeNode>();
        while((current!=null)||(stack.isEmpty())){
            if(current!=null){
                System.out.println(current.getInfo());
                stack.push(current);
                current = current.lchild;
            }else{
                current = stack.peek();
                stack.pop();
                current = current.rchild;
            }
        }
    }
    /**
     * 中序非递归
     * @param current
     */
    public void inOrderNonRecursive(BinaryTreeNode current){
        Stack<BinaryTreeNode> stack = new Stack<BTree.BinaryTreeNode>();
        while((current!=null)||(stack.isEmpty())){
            if(current!=null){
                stack.push(current);
                current = current.lchild;
            }else{
                current = stack.peek();
                stack.pop();
                System.out.println(current.getInfo());
                current = current.rchild;
            }
        }
    }
    /**
     * 后续非递归
     * @param current
     */
    public void postOrderNonRecursive(BinaryTreeNode current){
        Stack<BinaryTreeNode> stack = new Stack<BTree.BinaryTreeNode>();
        while((current!=null)||(stack.isEmpty())){
            if(current!=null){
                current.isFirst = true;
                stack.push(current);
                current = current.lchild;
            }else{
                current = stack.peek();
                stack.pop();
                if(current.isFirst){
                    current.isFirst = false;
                    stack.push(current);
                    current = current.rchild;
                }else{
                    System.out.println(current.getInfo());
                    current = null;
                }
            }
        }
    }
    
    public void bfs(BinaryTreeNode current){
        Queue<BinaryTreeNode> queue = new LinkedList<BTree.BinaryTreeNode>();
        while((current!=null)||queue.isEmpty()){
            if(current!=null){
                System.out.println(current.getInfo());
                queue.add(current.lchild);
                queue.add(current.rchild);
                current = queue.poll();
            }else{
                current = queue.poll();
            }
        }
    }
    
    
    public class BinaryTreeNode{
        private BinaryTreeNode lchild = null;
        private BinaryTreeNode rchild = null;
        private int info;
        private boolean isFirst;
        public int getInfo() {
            return info;
        }
        public void setInfo(int info) {
            this.info = info;
        }
    }
    
}