How do I practice coding and algorithm questions?

Use PracHub's coding console to write, test, and debug your solutions in Python or JavaScript. View hints, test against sample inputs, and compare with official solutions.

What difficulty level is this coding question?

This is a Medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at TikTok.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at TikTok during technical interviews.

Compute waits and find distance-k node pairs

Quick Overview

This question evaluates proficiency in algorithm design and data structure usage for both array and tree problems and falls under the Coding & Algorithms domain; it is commonly asked to assess algorithmic thinking, time and space complexity reasoning, and robustness in handling edge cases.

Company: TikTok

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: Medium

Interview Round: Technical Screen

Part 1 — Array next-higher wait: Given an integer array A where A[i] is the measurement for day i (0-indexed), return an array W of the same length such that W[i] is the smallest positive number d where i + d < n and A[i + d] > A[i]. If no such day exists, set W[i] = 0. Aim for an O(n) time solution and justify its correctness and space usage. Part 2 — Binary tree distance-k pairs: Given a binary tree with unique node values and an integer k ≥ 0, define the distance between two nodes u and v as follows: if one is an ancestor of the other, the distance is the number of intermediate nodes on the path between them; otherwise, it is the sum of their distances to their lowest common ancestor. Return the set of all unordered pairs (u, v), u ≠ v, whose distance equals k. Design an algorithm faster than O(n^ 2), describe the data structures you would use, analyze time and space complexity, and discuss edge cases such as k = 0 or an empty tree.

Quick Answer: This question evaluates proficiency in algorithm design and data structure usage for both array and tree problems and falls under the Coding & Algorithms domain; it is commonly asked to assess algorithmic thinking, time and space complexity reasoning, and robustness in handling edge cases.

Next Higher Waits

For each index, return the distance to the next later value that is strictly higher, or 0 if none exists.

Constraints

Inputs are provided as Python literals matching the function signature.
Return a deterministic exact-match result.

Examples

Input: ([73,74,75,71,69,72,76,73],)

Expected Output: [1, 1, 4, 2, 1, 1, 0, 0]

Explanation: Daily-temperatures style.

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

Expected Output: [0, 0, 0]

Explanation: No higher future value.

Input: ([],)

Expected Output: []

Explanation: Empty input.

Hints

Choose a representation that makes the core operation simple.
Handle empty and boundary inputs before the main algorithm.

Binary Tree Node Pairs at Distance K

Given unique level-order tree values and k, return sorted unordered value pairs whose standard edge distance is exactly k.

Constraints

Inputs are provided as Python literals matching the function signature.
Return a deterministic exact-match result.

Examples

Input: ([1,2,3,4,5,6,7], 2)

Expected Output: [[1, 4], [1, 5], [1, 6], [1, 7], [2, 3], [4, 5], [6, 7]]

Explanation: Pairs two edges apart.

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

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

Explanation: Adjacent pairs.

Input: ([], 1)

Expected Output: []

Explanation: Empty tree.

Input: ([1], 0)

Expected Output: []

Explanation: No pair with same node.

Hints

Choose a representation that makes the core operation simple.
Handle empty and boundary inputs before the main algorithm.

Quick Overview