[LeetCode] 102. Binary Tree Level Order Traversal - 문제풀이
Description 주어진 트리를 층별로 순회하며 순서대로 층별 요소의 목록을 반환하는 문제입니다. Given the root of a binary tree, return the level order traversal of its nodes' values. (i.e., from left to right, level by level). Example 1: Input: root = [3,9,20,null,null,15,7] Output: [[3],[9,20],[15,7]] Example 2: Input: root = [1] Output: [[1]] Example 3: Input: root = [] Output: [] Constraints: The number of nodes in the tree is in..