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。
LeetCode
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
286. Walls and Gates
286. Walls and Gates
題目給定一個矩陣，矩陣內有標記了牆與門，剩餘的點被標註成一個無限大的數值，意義為可以行走的點，要求把這些矩陣中除了門與牆以外的點，以該點到達附近最近的門的距離為何？
590. N-ary Tree Postorder Traversal
590. N-ary Tree Postorder Traversal
"""
# Definition for
144. Binary Tree Preorder Traversal
144. Binary Tree Preorder Traversal
# Definition for a binary tree
297. Serialize and Deserialize Binary Tree
297. Serialize and Deserialize Binary Tree
這一題可以透過 536. Construct Binary
677. Map Sum Pairs
667. Map Sum Pairs
class TrieNode:
def __init__(self, val
588. Design In-Memory File System
588. Design In-Memory File System
class TrieNode:
def __init__(self)
19. Remove Nth Node From End of List
19. Remove Nth Node From End of List
這一題我的第一個想法是我先走一趟算出整個 Linked
1095. Find in Mountain Array
1095. Find in Mountain Array