199. 二叉树的右视图
给定一棵二叉树,想象自己站在它的右侧,按照从顶部到底部的顺序,返回从右侧所能看到的节点值。
示例:
输入: [1,2,3,null,5,null,4]
输出: [1, 3, 4]
解释:
1 <---
/ \
2 3 <---
\ \
5 4 <---
思路
用二叉树的层序遍历,然后取每一层的最右边。
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def rightSideView(self, root):
"""
:type root: TreeNode
:rtype: List[int]
"""
nodeQuen = []
res = []
if not root:
return res
nodeQuen.append(root)
while nodeQuen:
level = []
for i in range(len(nodeQuen)):
crru = nodeQuen.pop(0)
if crru.left:
nodeQuen.append(crru.left)
if crru.right:
nodeQuen.append(crru.right)
level.append(crru.val)
res.append(level[-1])
return res