145. Binary Tree Postorder Traversal 145. Binary Tree Postorder Traversal # Definition for a binary tree
255. Verify Preorder Sequence in Binary Search Tree 255. Verify Preorder Sequence in Binary Search Tree 遞迴(超時)
114. Flatten Binary Tree to Linked List 114. Flatten Binary Tree to Linked List 這一是後續遍歷很經典的一道題目,體現了後續遍歷很重要的一個精神,當後續遍歷到一半,
429. N-ary Tree Level Order Traversal 429. N-ary Tree Level Order Traversal 可以先做這題 116. Populating Next
417. Pacific Atlantic Water Flow 417. Pacific Atlantic Water Flow 廣度優先搜索 BFS 也可以利用一次把多個點加入 queue 後再開始出發,