LeetCode222-完全二叉树的节点个数

原题链接：https://leetcode-cn.com/problems/count-complete-tree-nodes/

解题思路：树形DP

代码：

 1 # Definition for a binary tree node.
 2 # class TreeNode:
 3 #     def __init__(self, val=0, left=None, right=None):
 4 #         self.val = val
 5 #         self.left = left
 6 #         self.right = right
 7 class Solution:
 8     def countNodes(self, root: TreeNode) -> int:
 9         if not root:
10             return 0
11         return self.process(root)
12 
13     def process(self, x: TreeNode) -> int:
14         if not x:
15             return 0
16         left_cnt = self.process(x.left)
17         right_cnt = self.process(x.right)
18         return left_cnt + right_cnt + 1

 

相关问题：

如何判断一个树为完全二叉树

解题思路：树形DP

代码：

 1 class TreeNode:
 2     def __init__(self, val=0, left=None, right=None):
 3         self.val = val
 4         self.left = left
 5         self.right = right
 6 
 7 class ReturnData:
 8     def __init__(self, height, nodes):
 9         self.height = height
10         self.nodes = nodes
11 
12 def process(x: TreeNode) -> ReturnData:
13     if not x:
14         return ReturnData(0, 0)
15     leftData = process(x.left)
16     rightData = process(x.right)
17     
18     height = max(leftData.height, rightData.height) + 1
19     nodes = leftData.nodes + rightData.nodes + 1
20     return ReturnData(height, nodes)
21 
22 def is_cbt(root: TreeNode) -> bool:
23     res = process(root)
24     if res.nodes == 1 >> res.height - 1:
25         return True
26     return False

 

posted @ 2022-01-13 21:46  CaptainDragonfly  阅读(19)  评论(0)  编辑  收藏  举报