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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Flip a specific bit in an integer
Given a non-negative integer num and a zero-based bit position p, return the integer resulting from flipping only the bit at position p (i.e., 0 becom...
Evaluate arithmetic expression with precedence
Question Implement an evaluator for a string arithmetic expression. The input contains non-negative integers, the operators +, -, `, /, parentheses ( ...
Solve PTO window and sparse unique counting
Solve PTO window and sparse unique counting Design algorithms for two problems: A) Longest vacation with limited PTO: Given an array A of characters w...
Parse and evaluate nested expressions with validation
Design and implement a parser/evaluator for a parenthesized expression language where the input string may be invalid. The language uses spaces as tok...
Compute shortest recursive string encoding
Given a string s, compress it by replacing any consecutive repetition of a substring with the form k{pattern} where k > 1 and pattern may itself be re...
Compute max simultaneous drivers last 24 hours
Given delivery intervals (driverId, startTime, endTime) already recorded, implement maxSimultaneousDriverInPast24Hours() that returns the maximum numb...
Evaluate arithmetic expression using DFS
Given a string representing an arithmetic expression with non-negative integers, +, -, *, /, parentheses, and optional spaces, evaluate its value. Use...
Optimize file reads for password validation
Given a multi-gigabyte credentials file on disk with one record per line in the format user_id,salt,password_hash (hex), implement validate(user_id, p...
Compare Spring and Spring Boot
Compare Spring and Spring Boot What are the differences between Spring Framework and Spring Boot? Compare configuration approaches, auto-configuration...
Decide reachability with buses and limited walking
You are given: ( 1) a start point (xs, ys), ( 2) an end point (xe, ye), ( 3) an integer K, and ( 4) an undirected graph of bus stations where each nod...
Compute ring window max and deletion indices
Part A — Ring window maximum: You are given n computers arranged in a circle, represented by an array of bits (1 = on, 0 = off), and an integer k (1 <...
Solve BFS grid delivery routing
You are given an m×n grid representing a city: 'S' are DashMart stores, 'H' are homes, '.' are roads, and '#' are obstacles. Movement is allowed in fo...
Compute sliding-window medians
Given an array nums and an integer k, compute the median for each contiguous subarray (window) of length k and return the sequence of medians in order...
Check diagonal equality in a matrix
Given an m x n integer matrix, determine whether every top-left to bottom-right diagonal contains identical values (all elements along each such diago...
Implement 64-bit modular exponentiation safely
Implement a function to compute (a^b) mod m where 0 ≤ a,b < 2^61−1 and 1 ≤ m < 2^61−1 using only 64-bit operations without overflow. Provide implement...
Merge overlapping time intervals efficiently
Given a list of closed intervals [start, end] with 0 <= start <= end, merge all intervals that overlap or touch and return a minimal set of non-overla...
Design test logging and failure-window queries
Build an in-memory service to log test run results and answer two queries. Assumptions: events arrive with strictly increasing timestamps across all t...
Minimum Time to Run All Jobs with a Cooldown Between Identical Jobs
You are given a list of jobs to run on a single-core CPU, where each job is represented by an uppercase letter 'A'–'Z' in an array jobs. Jobs of the s...
Implement basic calculator
Question LeetCode 227. Basic Calculator II – implement an arithmetic expression evaluator supporting +, -, *, / and integer operands https://leetcode....
Solve LeetCode string and list problems
Question LeetCode 767. Reorganize String LeetCode 23. Merge k Sorted Lists LeetCode 138. Copy List with Random Pointer https://leetcode.com/problems/r...