Given the root of a binary tree, return the preorder traversal of its nodes' values.
- code
class Solution:
def preorderTraversal(self, root: TreeNode) -> List[int]:
self.res = []
def pre(root):
if root:
self.res.append(root.val)
pre(root.left)
pre(root.right)
pre(root)
return self.res
- code
class Solution:
def preorderTraversal(self, root):
ret = []
stack = [root]
while stack:
node = stack.pop()
if node:
ret.append(node.val)
stack.append(node.right)
stack.append(node.left)
return ret