Coding & Algorithms Interview Questions
Practice 3,469 real Coding & Algorithms interview questions for 2026. Covers companies like Meta, Amazon, Google, Uber, and Microsoft. Real questions from actual interviews with detailed solutions — ideal for focused interview preparation. Coding & Algorithms interview questions are the single most common technical gate for software engineering roles and are used to evaluate problem framing, algorithm selection, complexity trade-offs, correctness, edge-case reasoning, and clear communication under time pressure. Expect this category to appear in early technical screens and repeatedly across onsite loops at companies that weight it heavily (notably Meta, Google, and Amazon). Interviews will test arrays and strings, trees and graphs, dynamic programming, hashing and two‑pointer techniques, and the candidate’s ability to test and optimize code in a shared editor. Prepare with timed mock interviews, practice in the same editor you’ll use live, and build a progressive schedule that moves from fundamentals to medium/hard problems; typical candidates invest several weeks to a few months of focused practice depending on seniority and target company.
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Min deletions to avoid overlap in first k
This question evaluates array and sequence manipulation skills, set-based reasoning about value overlap, and the ability to compute minimal edits whil...
Multi-Level Warehouse Storage with Weighted Retrieval
Multi-Level Warehouse Storage with Weighted Retrieval You are building the in-memory engine for an automated warehouse. The warehouse is a stack of ho...
Solve Matrix, Tree, Nested, LCA, Maze Tasks
Answer the following independent coding tasks. For each task, implement a clean API, handle edge cases, and analyze time and space complexity. 1. Trav...
Find Shortest Grid Path
You are given an m x n grid where 0 represents an open cell and 1 represents a blocked cell. You are also given a start cell (sr, sc) and a target cel...
Implement encode/decode for list of strings
You are given a list of strings (may include digits and symbols). Implement two methods: - encode(List<String> input) -> String: converts the list int...
Maximize concatenation length with unique chars
This question evaluates understanding of string manipulation, set-based uniqueness constraints, and combinatorial subset selection for maximizing conc...
Check if each prefix forms 1..k permutation
You are given an integer array arr of length n that is a permutation of the numbers 1..n (each number appears exactly once), but in arbitrary order. F...
Compute product of array except self
This question evaluates understanding of array manipulation, modular arithmetic, and algorithmic optimization by requiring computation of per-element ...
Find minimum reversals to orient edges away from root
You are given a connected graph with n nodes labeled 0..n-1 and n-1 directed edges. If you ignore edge directions, the edges form a tree. Each directe...
Compute final prices with next smaller discount
You are given an integer array prices of length n, where prices[i] is the original price of the i-th item. For each item i, find the first index j > i...
Implement LRU/LFU cache with custom eviction
This question evaluates proficiency in cache design and data-structure implementation, focusing on eviction policies (LRU, LFU), metadata tracking for...
Implement worker time and payroll tracker
This question evaluates skills in designing in-memory data structures and algorithms for temporal event handling, interval arithmetic, stateful toggle...
Implement idempotent request handling with idempotency keys
This question evaluates understanding of idempotency semantics, idempotency-key handling, concurrency control, synchronization, and in-memory TTL-base...
Design dynamic weighted random sampling with updates
Problem: Support weighted random sampling with insert/delete Design a data structure that maintains a dynamic set of items, each with a positive integ...
Count visible people to the right
Problem You are given an array heights of length n, where heights[i] is the height of the i-th person standing in a line from left to right. For each ...
Delete nodes in linked list and binary tree
You are asked to solve two short coding tasks. You may assume standard node definitions: - Singly linked list node: val, next - Binary tree node: val,...
Implement an LFU cache with O(1) operations
This question evaluates a candidate's ability to design and implement efficient data structures for caching, including understanding frequency-based e...
Implement a lazy inorder traversal iterator
This question evaluates understanding of binary tree traversal and iterator design, specifically the implementation of a lazy inorder iterator under t...
Count subarrays with sum equals k
This question evaluates a candidate's competency in array algorithms and reasoning about contiguous subarray sums, including correct handling of negat...
Extend cloud file system with copy and compression
In-Memory Cloud File System V2: Copy, Capacity Updates, Compress/Decompress Design an in-memory file system with per-user quotas and additional operat...