Binary Tree Level Order Traversal

Problem

Return tree node values grouped by level, using a complete-index level-order array.

Examples

Example 1

Input: [3,9,20,null,null,15,7]

Output: [[3],[9,20],[15,7]]

Example 2

Input: [1,2,3]

Output: [[1],[2,3]]

Input and output use JSON-compatible values. For linked-list and tree questions, arrays represent the node structure as described above. Your code should implement solve(input).

Write your solutionImplement solve(input). Your draft is saved in this browser.

Compiler

How to solve Binary Tree Level Order Traversal

Return tree node values grouped by level, using a complete-index level-order array. Breadth-first traversal naturally groups nodes by depth. The reference implementation illustrates this approach; check the example and edge cases.

Time and space complexity

O(n) time and O(n) queue space.

Practise and improve

Choose JavaScript, TypeScript or Python, complete the starter code, then select Run Tests. Request a hint when you need guidance, or choose View solution and confirm if you would like to study the reference implementation.