LeetCode199 Binary Tree Right Side View
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LeetCode199 Binary Tree Right Side View
问题来源LeetCode199
问题描述
Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.
For example:
Given the following binary tree, 1 <--- / \2 3 <--- \ \ 5 4 <---You should return [1, 3, 4].
这道题就是假设你站在二叉树的右边,返回能够看到的节点的值。
问题分析
这道题其实就是对树进行层遍历,然后保存每层最后一个元素的值。层遍历实现的方法很多,这里我用的是队列。最后出列的元素就是该层的最后一个元素。
代码如下
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */public List<Integer> rightSideView(TreeNode root) { List<Integer> res = new ArrayList<>(); if(root==null) return res; Queue<TreeNode> queue = new ArrayDeque<>(); Queue<TreeNode> queue2 = new ArrayDeque<>(); queue.add(root); while (!queue.isEmpty()){ TreeNode node =queue.poll(); if(node.left!=null) queue2.add(node.left); if(node.right!=null) queue2.add(node.right); if(queue.isEmpty()){ res.add(node.val); queue=queue2; queue2=new ArrayDeque<>(); } } return res;}
LeetCode学习笔记持续更新
GitHub地址 https://github.com/yanqinghe/leetcode
CSDN博客地址 http://blog.csdn.net/yanqinghe123/article/category/7176678
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