144. Binary Tree Preorder Traversal
Easy
Given the root of a binary tree, return the preorder traversal of its nodes' values
class Solution:
def preorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
if root is None:
return []
return (
[root.val]
+ self.preorderTraversal(root.left)
+ self.preorderTraversal(root.right)
)
class TreeNode(object):
def __init__(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right