144. Binary Tree Preorder Traversal
Easy
10 Points
Stack
Tree
Depth-First Search
Binary Tree
Given the root of a binary tree, return the preorder traversal of its nodes' values.
Examples
Example 1
Input: root = [1,null,2,3]
Output: [1,2,3]
Explanation:
Example 2
Input: root = [1,2,3,4,5,null,8,null,null,6,7,9]
Output: [1,2,4,5,6,7,3,8,9]
Explanation:
Example 3
Input: root = []
Output: []
Example 4
Input: root = [1]
Output: [1]
Constraints
The number of nodes in the tree is in the range [0, 100].-100 <= Node.val <= 100
Follow Up
- Recursive solution is trivial, could you do it iteratively?
144. Binary Tree Preorder Traversal
Easy
10 Points
Stack
Tree
Depth-First Search
Binary Tree
Given the root of a binary tree, return the preorder traversal of its nodes' values.
Examples
Example 1
Input: root = [1,null,2,3]
Output: [1,2,3]
Explanation:
Example 2
Input: root = [1,2,3,4,5,null,8,null,null,6,7,9]
Output: [1,2,4,5,6,7,3,8,9]
Explanation:
Example 3
Input: root = []
Output: []
Example 4
Input: root = [1]
Output: [1]
Constraints
The number of nodes in the tree is in the range [0, 100].-100 <= Node.val <= 100
Follow Up
- Recursive solution is trivial, could you do it iteratively?