449. Serialize and Deserialize BST
449. Serialize and Deserialize BST
參考 297. Serialize and Deserialize
Tree
124. Binary Tree Maximum Path Sum
124. Binary Tree Maximum Path Sum
這一題是後序遍歷的經典題目，後序遍歷的精神就是先將子樹的問題全部解決，再開始處理跟節點的問題，這一題要怎麼想到的確是屬於困難的題型。
106. Construct Binary Tree from Inorder and Postorder Traversal
106. Construct Binary Tree from Inorder and Postorder Traversal
postorder
94. Binary Tree Inorder Traversal
94. Binary Tree Inorder Traversal
# Definition for a binary tree
286. Walls and Gates
286. Walls and Gates
這題是 BFS 廣度優先搜索的題目，DFS 應該也可以做。
我一開始的做法是把
1373. Maximum Sum BST in Binary Tree
1371. Maximum Sum BST in Binary Tree
# Definition for a
222. Count Complete Tree Nodes
222. Count Complete Tree Nodes
線性搜索
# Definition for a binary
559. Maximum Depth of N-ary Tree
559. Maximum Depth of N-ary Tree
"""
# Definition for a Node.
261. Graph Valid Tree
DFS 搜尋的重點是，鄰居可以是 parent ，但是如果不是 parent 卻曾經造訪過，就代表這棵樹裡面有閉圈。
class Solution:
437. Path Sum III
437. Path Sum III
更難的樹的遍歷加上回溯法。
# Definition for a binary tree