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What difficulty level is this coding question?

This is a medium difficulty Coding & Algorithms question, commonly asked during Onsite rounds at Meta.

What role is this question designed for?

This question is commonly asked for Machine Learning Engineer candidates at Meta during technical interviews.

Solve frequency and tree-completeness problems

Quick Overview

These two problems evaluate competency in frequency counting and selection algorithms for identifying top-k elements and in binary tree structure analysis and traversal for checking completeness, belonging to the Coding & Algorithms domain and the broader data structures and algorithms category.

Company: Meta

Role: Machine Learning Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Onsite

## Problem A: Return the *k* most frequent values You are given an integer array `nums` and an integer `k`. **Task:** Return the `k` distinct values that occur most frequently in `nums`. **Input** - `nums`: list of integers (length `n`) - `k`: integer, `1 <= k <= (# of distinct values in nums)` **Output** - A list of `k` integers: the values with highest frequency. **Notes / Constraints** - If multiple answers are possible due to ties, any valid order is acceptable. - Aim for better than `O(n log n)` if possible. --- ## Problem B: Check whether a binary tree is complete You are given the `root` of a binary tree. A binary tree is **complete** if: 1. Every level except possibly the last is completely filled, and 2. All nodes in the last level are as far left as possible. **Task:** Return `true` if the tree is complete; otherwise return `false`. **Input** - `root`: root node of a binary tree (each node has `val`, `left`, `right`) **Output** - Boolean: whether the tree is complete. **Constraints** - Up to ~`10^5` nodes.

Quick Answer: These two problems evaluate competency in frequency counting and selection algorithms for identifying top-k elements and in binary tree structure analysis and traversal for checking completeness, belonging to the Coding & Algorithms domain and the broader data structures and algorithms category.

Top K Frequent Values

Return k distinct values with highest frequency, tie-breaking by value ascending for determinism.

Constraints

Inputs are Python literals matching the function signature.
Return a deterministic exact-match value.

Examples

Input: ([1,1,1,2,2,3], 2)

Expected Output: [1, 2]

Explanation: Classic example.

Input: ([4,4,5,5], 1)

Expected Output: [4]

Explanation: Tie by value.

Hints

Use deterministic tie-breaking for prompts with multiple valid outputs.
For design-style APIs, simulate operations with explicit inputs.

Check Complete Binary Tree

Given level-order values with None holes, return whether the binary tree is complete.

Constraints

Inputs are Python literals matching the function signature.
Return a deterministic exact-match value.

Examples

Input: ([1,2,3,4,5,6],)

Expected Output: True

Explanation: Complete.

Input: ([1,2,3,4,None,6,7],)

Expected Output: False

Explanation: Gap before node.

Input: ([],)

Expected Output: True

Explanation: Empty tree complete.

Hints

Use deterministic tie-breaking for prompts with multiple valid outputs.
For design-style APIs, simulate operations with explicit inputs.

Quick Overview