leetcode-199 二叉树的右视图 Python

最新推荐文章于 2022-05-05 19:32:17 发布

Xenonon

最新推荐文章于 2022-05-05 19:32:17 发布

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文章标签：二叉树 leetcode python 算法 stack

本文链接：https://blog.youkuaiyun.com/Xenonon/article/details/105682907

方法一：DFS

# 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]:
        rightmost_value_at_depth = dict()
        max_depth = -1

        stack = [(root, 0)]
        while stack:
            node, depth = stack.pop()

            if node is not None:
                max_depth = max(max_depth, depth)
                rightmost_value_at_depth.setdefault(depth, node.val)
                stack.append((node.left, depth+1))
                stack.append((node.right, depth+1))
        return [rightmost_value_at_depth[depth] for depth in range(max_depth + 1)]

方法二：BFS

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
from collections import deque
class Solution:
    def rightSideView(self, root: TreeNode) -> List[int]:
        rightmost_value_at_depth = dict()
        max_depth = -1
        queue = deque([(root, 0)])
        while queue:
            node, depth = queue.popleft()
            if node is not None:
                max_depth = max(max_depth, depth)
                rightmost_value_at_depth[depth] = node.val
                queue.append((node.left, depth + 1))
                queue.append((node.right, depth + 1))
        return [rightmost_value_at_depth[depth] for depth in range(max_depth+1)]