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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Determine if a string can be segmented
Given a string s and a list of strings wordDict, determine whether s can be segmented into a sequence of one or more dictionary words. - You may reuse...
Solve hierarchy distance and digit-square convergence
You have two independent tasks: A) Organization hierarchy distance Given a list of (employee, manager) pairs that form a complete hierarchy (a single ...
Count palindrome substrings in a string
Given a lowercase ASCII string s, count the number of substrings that are palindromes and return the count. Implement an O(n^ 2) solution using expand...
Design variable-size LRU cache
Implement an in-memory cache with least-recently-used eviction where each entry has a variable size in bytes. The cache exposes set(key, value, size),...
Design a balloon stability tracker
Implement a class BalloonFestival to manage hot-air balloons and wind fields over time, and to report rewarded balloons at inspection times. Methods a...
Segment a message with width-constrained suffixes
Given a message string s and an integer width W, split s into consecutive segments and append a suffix "i/n" to each segment indicating its 1-indexed ...
Design IP/CIDR rule matcher
Design and implement a rule matcher that returns 'accept' or 'deny' for a given IPv4 address based on a set of rules. Each rule can be either an inclu...
Design a nested transaction store
Implement an in-memory key–value store that supports nested transactions with the operations: SET key value, RETURN key, BEGIN, APPLY (commit current ...
Find top-k rated nodes via traversal
You are given a finite graph (directed or undirected) with n nodes and m edges. Each node u has an integer rating r[u]. Given a starting node s and an...
Implement binary search lower/upper bounds
Question Given a non-decreasing sorted integer array nums of length n and a target value, implement two functions using binary search: 1. lower_bound(...
Implement a Simple Banking Ledger
Design and implement a banking ledger for n accounts labeled 1..n with initial balances. Provide an API: deposit(id, amount) -> bool, withdraw(id, amo...
Design a menu manager with enums
Design and implement a console-based restaurant menu management program. Requirements: ( 1) There are exactly three fixed item categories represented ...
Design an in-memory file system with limits
Design and implement an in-memory hierarchical file system. Requirements: 1) addFile(String path): Given an absolute path like "path/to/somewhere/file...
Find minimum covering substring
Given two strings s and t, return the shortest contiguous substring of s that contains every character of t with at least the same multiplicities. If ...
Compute CDF from a PDF Function
You are given a callable function pdf(t) that returns the probability density of a normal distribution at value t. Implement a function cdf(x) that re...
Remove duplicates in-place from unsorted array
Problem You are given an array nums of unsorted integers. Write a method that removes duplicates in-place (i.e., without using any additional data str...
Compute dependency load factors in a DAG
System Dependency Load Factor You are given: - programs: a list of unique program names (strings) - prerequisites: a list of pairs [a, b] meaning prog...
Compute decayed power levels in a graph
You are given an unweighted graph representing a network of wires. - The graph has N nodes labeled 0..N-1 and M edges (each edge is a bidirectional wi...
Find max equal-frequency block count for each prefix
Given a string S of length n (e.g., uppercase letters), for every prefix P = S[0..i] (for i = 0..n-1), compute the maximum integer k such that: - The ...
Implement multi-head attention and LLM sampling
Task A: Multi-head attention (forward pass) You are implementing a Transformer attention layer. Given: - A sequence length L and model dimension d_mod...