刷题做项目记录贴

Apr 1, 2022
Binary Tree Traversal
早上默写：
- 199. Binary Tree Right Side View
- 102. Binary Tree Level Order Traversal
- 107. Binary Tree Level Order Traversal II
- 103. Binary Tree Zigzag Level Order Traversal

这几题都能用bfs + queue
- initialize res list and q queue
- use while loop to check if q is not empty
   - use for loop with range(qLen) to iterate through elements in each level of the tree
      - pop and store the node using popleft()
      - check if node exists, if it does
         - append its left and right children to the q

还是卡卡的，要注意：
- while loop 进下个level时要清空level list
- 在每个level要对pop出来的node进行操作前要先检查node 不为空