Binary Tree Level Order Traversal
Module 17 · Binary Trees
Problem
Given the root of a binary tree, return the values of its nodes as
level order traversal — grouped into a list of lists, one inner list
per level, left to right. (LeetCode 102.)
Examples
Example 1
Input
root = [3,9,20,null,null,15,7]Output[[3],[9,20],[15,7]]text
3
/ \
9 20
/ \
15 7Constraints
0 ≤ n ≤ 2000 nodes
Attempt it first
This is a direct, unmodified application of the BFS & Level-Order Traversal concept lesson — the exercise is confirming you can reproduce the level-boundary technique (snapshotting the queue's size at the start of each level) without re-deriving it. Try writing it before opening anything.