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 <---
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/binary-tree-right-side-view
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使用DFS算法可得
# 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: TreeNode) -> List[int]:
rightside = dict()
stack = [(root,0)]
maxdepth = -1
while stack:
node,depth = stack.pop()
if node is not None:
maxdepth = max(maxdepth,depth)
rightside.setdefault(depth,node.val)
stack.append((node.left,depth+1))
stack.append((node.right,depth+1))
return [rightside[i] for i in range(maxdepth+1)]