LC 0144 [M] Binary Tree Preorder Traversal
Code with Senpai edited this page Jun 2, 2020
·
2 revisions
it's like level-order with a queue, but just use a stack
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def preorderTraversal(self, root: TreeNode) -> List[int]:
if not root: return []
res = []
s = []
s.append(root)
while s:
node = s.pop()
res.append(node.val)
if node.right:
s.append(node.right)
if node.left:
s.append(node.left)
return res
footer