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 easy difficulty Coding & Algorithms question, commonly asked during Onsite rounds at TikTok.

What role is this question designed for?

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

Solve three classic coding problems | TikTok Coding Question

Quick Overview

These tasks evaluate algorithmic problem-solving, data structure mastery, and implementation skills within the Coding & Algorithms domain, touching on dynamic programming (longest increasing subsequence), order-statistics in sorted arrays, tree pointer manipulation for perfect binary trees, and graph traversal for connected components.

Solve three classic coding problems

Company: TikTok

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: easy

Interview Round: Onsite

You are given three independent coding tasks. Implement a function for each. ## 1) Longest Increasing Subsequence (LIS) Given an integer array `nums`, return the length of the longest **strictly increasing** subsequence. - **Input:** `nums` (array of integers) - **Output:** integer length of the LIS - **Constraints (typical):** `1 <= n <= 2e5` (or smaller), values fit in 32-bit signed int ## 2) k-th Largest Element in Two Sorted Arrays Given two arrays `A` and `B`, each sorted in **non-decreasing** order, and an integer `k` (1-indexed), return the **k-th largest** element in the multiset union of `A` and `B`. - **Input:** `A`, `B` (sorted arrays), `k` - **Output:** the k-th largest element - **Notes:** Arrays may have different lengths; duplicates are allowed. - **Constraints (typical):** `0 <= len(A), len(B) <= 2e5`, `1 <= k <= len(A)+len(B)` ## 3) Connect Nodes at the Same Tree Level Given a **perfect** binary tree (all internal nodes have exactly two children and all leaves are at the same depth), populate each node’s `next` pointer so it points to its immediate neighbor to the right on the same level. If there is no neighbor, set `next = null`. - **Input:** root of a perfect binary tree with fields `left`, `right`, `next` - **Output:** the root (after pointers are populated) - **Requirement (typical):** use `O(1)` extra space (excluding recursion stack) ## 4) Number of Islands Given an `m x n` grid of characters containing `'1'` (land) and `'0'` (water), return the number of **connected components** of land. Cells are connected **4-directionally** (up/down/left/right). - **Input:** `grid` (2D array of `'0'`/`'1'`) - **Output:** integer number of islands - **Constraints (typical):** `1 <= m,n <= 200` (or similar)

Quick Answer: These tasks evaluate algorithmic problem-solving, data structure mastery, and implementation skills within the Coding & Algorithms domain, touching on dynamic programming (longest increasing subsequence), order-statistics in sorted arrays, tree pointer manipulation for perfect binary trees, and graph traversal for connected components.

Longest Increasing Subsequence Length

Return the length of the longest strictly increasing subsequence.

Constraints

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

Examples

Input: ([10,9,2,5,3,7,101,18],)

Expected Output: 4

Explanation: Classic example.

Input: ([7,7,7],)

Expected Output: 1

Explanation: Strictly increasing rejects equals.

Input: ([],)

Expected Output: 0

Explanation: Empty array.

Hints

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

K-th Largest in Two Sorted Arrays

Given two non-decreasing arrays and 1-indexed k, return the k-th largest value in their multiset union.

Constraints

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

Examples

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

Expected Output: 5

Explanation: Second largest.

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

Expected Output: 2

Explanation: Duplicates count.

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

Expected Output: 5

Explanation: One empty array.

Hints

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

Serialize Next Pointers by Level

For a perfect binary tree represented as level-order values, return each level as [node,next] pairs after connecting next pointers left to right.

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],)

Expected Output: [[[1, None]], [[2, 3], [3, None]], [[4, 5], [5, 6], [6, 7], [7, None]]]

Explanation: Three-level perfect tree.

Input: ([1],)

Expected Output: [[[1, None]]]

Explanation: Single node.

Hints

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

Number of Islands

Count four-directionally connected land regions in a binary grid.

Constraints

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

Examples

Input: ([['1','1','0'], ['0','1','0'], ['1','0','1']],)

Expected Output: 3

Explanation: Three islands.

Input: ([],)

Expected Output: 0

Explanation: Empty grid.

Hints

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

Quick Overview