Description
Difficulty: 中等
Related Topics: Tree, Breadth-First Search, Binary Tree
Given the root of a binary tree, return the bottom-up level order traversal of its nodes’ values. (i.e., from left to right, level by level from leaf to root).
Example 1:
Input: root = [3,9,20,null,null,15,7]
Output: [[15,7],[9,20],[3]]Example 2:
Input: root = [1]
Output: [[1]]Example 3:
Input: root = []
Output: []Constraints:
- The number of nodes in the tree is in the range
[0, 2000]. -1000 <= Node.val <= 1000
Solution
Language: Go
IOI
