Coding & Algorithms Interview Questions
Practice 3,013 real Coding & Algorithms interview questions for 2026. Coding & Algorithms interview questions for top tech firms like Meta, Amazon, Google, Uber, and TikTok — real questions from actual interviews with detailed solutions — to power your interview preparation. This collection is sharply focused on algorithmic patterns (arrays, strings, sliding windows, trees/graphs, dynamic programming, greedy, two-pointers, and hashing), clean, review-ready code, and the explanation skills that distinguish hires. In 2026 expect familiar medium-to-hard problems plus newer twists: AI-enabled or multi-file coding rounds at some companies, more emphasis on explainability and edge-case reasoning, and occasional real-world performance constraints (streaming, concurrency, memory limits). Interviewers evaluate problem framing, algorithm choice, complexity trade-offs, test-case thinking, and communication under time pressure. Best prep mixes pattern-based practice, timed mock interviews, code-review style polishing, and rehearsed explanations of complexity and tradeoffs. Focus your last-mile prep on writing correct, readable code quickly and on explaining why your solution is robust and efficient for production scenarios.

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"Discovered PracHub 10 days before my interview. By day 5, I stopped being nervous. By interview day, I was actually excited to show what I knew."

"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
Implement an ASCII Art Printer
Implement an ASCII art printer. A font defines each supported character as a glyph with the same height. A glyph is a list of equal-length text rows. ...
Find mode in a trinary search tree
You are given the root of a trinary search tree where each node has up to three children: `text class Node { int val; Node left; // all values ...
Solve interval merge and string dedup problems
You are given three coding questions from a phone screen. Solve each independently. 1) Merge overlapping intervals Input: A list of intervals interval...
Find Banks From Identifier Mappings
Plaid receives institution metadata from multiple sources. You are given two mappings: 1. code_to_institution: a one-to-one mapping from a bank code t...
Solve Linked-List and Iterator Problems
You are asked to solve two coding problems. Problem 1: Detect shared nodes between possibly cyclic linked lists You are given the heads of two singly ...
Determine Complete Interval Coverage
You need to process a stream of real-valued points on a one-dimensional target segment from 0 to 50. Each time a point x arrives, it contaminates the ...
Solve sliding-window and disjoint-string-pairs tasks
Task A (Sliding Window) Given a string s, find the length of the longest contiguous substring that contains no repeated characters. - Input: a string ...
Solve Four Online Assessment Problems
Complete the following four independent coding tasks. For each task, write a function that returns the requested result. 1. Find the best value index ...
Implement flood fill using BFS and DFS
Problem You are given a 2D grid image of size m × n, where each cell contains an integer color value. You are also given a starting cell (sr, sc) and ...
Filter ads by a single rule
Single-Rule Ad Filter Context When a user watches content, the system needs to filter an ad pool to find ads that match one rule. Implement a lightwei...
Merge K timestamped lists with timestamp coalescing
You are given k sorted lists (or linked lists) of records. Each record has: - timestamp (integer) - values (an array of integers sorted in non-decreas...
Remove adjacent duplicates and handle tree input
You are asked three related coding questions. 1) Remove adjacent duplicates (repeatedly) Given a string s (lowercase English letters), repeatedly remo...
Compute max profit across dated stock quotes
You are given an unsorted list of price records for multiple stocks, each record as (date, symbol, price). Dates may be repeated across different symb...
Implement stack variants and path-sum check
Coding tasks Solve the following algorithmic problems. 1) MinStack Design a stack supporting: - push(x), pop(), top() - getMin() returning the minimum...
Solve two coding assessment tasks
The online assessment contained two coding problems: 1. Maximize store revenue You are given an integer array quantity of length n, where quantity[i...
Implement bus route simulation features
Bus Route Simulation – Boarding, Capacity, and Priority Passes You are given a partially implemented codebase for simulating bus routes in a city. Bus...
Merge two sorted arrays in-place
You are given two integer arrays sorted in non-decreasing order, and two integers m and n: - nums1 has length m + n. The first m elements of nums1 con...
Maximize revenue by choosing one query type
You are given a virtual warehouse that can execute queries. There are n query types, and you must choose exactly one query type to run repeatedly for ...
Decompress encoded string with nested repeats
Given an encoded string, decompress it into its expanded form. Encoding rules: - Parentheses (...) denote a group. - A repetition count is written in ...
Answer suffix maximum-frequency queries
You are given: - An integer array nums of length n. - An integer array queries of length m, where each queries[k] is an index i (0-based) into nums. F...