https://leetcode.com/problems/binary-tree-preorder-traversal/
Given the root of a binary tree, return the preorder traversal of its nodes' values.
root
Input: root = [1,null,2,3] Output: [1,2,3]
# Definition for a binary tree node. # class TreeNode: # def __init__(self, val=0, left=None, right=None): # self.val = val # self.left = left # self.right = right class Solution: def preorderTraversal(self, root: TreeNode) -> List[int]: to_ret = [] def preorder(root): if not root: return to_ret.append(root.val) preorder(root.left) preorder(root.right) preorder(root) return to_ret
If the root node does not exist, return nothing.
Else perform preorder by:
Appending the value
Left recurse
Right recurse
Last updated 3 years ago
Example 1: