Description:
Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).
For example:
Given binary tree [3,9,20,null,null,15,7],
return its level order traversal as:
Solution:
class Solution:
def levelOrder(self, root: TreeNode) -> List[List[int]]:
if root == None:
return []
node_ls = [root]
value_ls = []
value_cache = [root.val]
def helper(node_ls):
cache = []
for node in node_ls:
if node != None:
cache.append(node.left)
cache.append(node.right)
return cache
while value_cache:
value_ls.append(value_cache)
node_ls = helper(node_ls)
value_cache = [n.val for n in node_ls if n != None]
return value_ls
Runtime: 40 ms, faster than 82.05% of Python3 online submissions for Binary Tree Level Order Traversal.
Memory Usage: 13.5 MB, less than 39.42% of Python3 online submissions for Binary Tree Level Order Traversal.
