leetcode：Flatten Binary Tree to Linked List 【Java】

二叉树展平为链表

最新推荐文章于 2022-07-27 15:08:45 发布

tterminator

最新推荐文章于 2022-07-27 15:08:45 发布

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分类专栏： leetcode 文章标签： leetcode

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本文介绍了一种将二叉树结构通过特定算法展平为链表的方法。该方法利用栈结构进行节点遍历，并调整每个节点的左右子节点指向，最终使二叉树变为按先序遍历顺序连接的链表。

一、问题描述

Given a binary tree, flatten it to a linked list in-place.

For example,
Given

The flattened tree should look like:

click to show hints.

Hints:

If you notice carefully in the flattened tree, each node's right child points to the next node of a pre-order traversal.

二、问题分析

mark：参照了网上代码。

三、算法代码

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public void flatten(TreeNode root) {
        if(root == null){
            return;
        }
        
        Stack<TreeNode> stack = new Stack<TreeNode>();
        stack.push(root);
        TreeNode p = null;
        while(!stack.empty()){
            p = stack.peek();
            stack.pop();
            
            if(p.right != null){
                stack.push(p.right);
            }
            if(p.left != null){
                stack.push(p.left);
            }
            
            p.left = null;
            if (!stack.empty())
                p.right = stack.peek();
            
        }
    }
}