543. Diameter of Binary Tree
Đề Bài
Given the root of a binary tree, return the length of the diameter of the tree.
The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.
The length of a path between two nodes is represented by the number of edges between them.
Example 1:
Input: root = [1,2,3,4,5] Output: 3 Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].
Example 2:
Input: root = [1,2] Output: 1
Constraints:
- The number of nodes in the tree is in the range
[1, 104]. -100 <= Node.val <= 100
Thuật Toán & Kỹ Thuật
⏱️ Thời gian
O(V+E)
💾 Không gian
O(V)
Lời Giải
Python
0543-diameter-of-binary-tree.py
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def dfs(self, root):
if not root:
return 0
longestLeft = self.dfs(root.left)
longestRight = self.dfs(root.right)
self.longest = max(self.longest, longestLeft + longestRight)
return max(longestLeft, longestRight) + 1
def diameterOfBinaryTree(self, root: Optional[TreeNode]) -> int:
self.longest = 0
self.dfs(root)
return self.longest