Coding & Algorithms Interview Questions
Practice 3,429 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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Detect shuffle-mode sequence
Question Given a playlist of distinct songs and two player modes—Random (each next song chosen independently and uniformly at random, with replacement...
Find names similar by one swap
Question LeetCode 859. Buddy Strings – Given a target string and a list of strings, return all list entries that can match the target by swapping at m...
Check Palindrome and Add Decimal Strings
Question LeetCode 266. Palindrome Permutation – Given a string, determine whether any permutation can form a palindrome. Follow-up: If a palindrome pe...
Design timestamped key-value map
Question Design a class that supports insert(key, value, timestamp) and get(key, timestamp) where get returns the value whose timestamp is the smalles...
Explain and Implement Strings
Question What is a string in programming languages? Inside a struct string{} in Rust, what fields are stored and how would you design and implement on...
Handle palindrome & decimal addition
Question LeetCode 266. Palindrome Permutation Given two non-negative decimal number strings, implement addition that supports a decimal point. https:/...
Explain strings and copy complexity
Question What is a string? What fields does a struct string contain, and how would you implement it yourself? What is the time complexity of copying a...
Explain strings, moves, and concurrency
Question What is a string in programming languages? What fields are stored in a typical struct string and how would you implement one yourself? What i...
Solve vertical order & diameter variants
Question LeetCode 314. Binary Tree Vertical Order Traversal LeetCode 543. Diameter of Binary Tree – modified to return the number of nodes (edges + 1)...
Round numeric string values
Question Given a numeric string, implement rounding to the nearest integer (e.g., '3.5' → '4', '100.01' → '100'). Follow-up: round to the last signifi...
Solve array and list algorithms
Question LeetCode 315. Count of Smaller Numbers After Self LeetCode 23. Merge k Sorted Lists Design algorithm for Amazon Locker getPackage (retrieve p...
Compute minimum passes to collect numbers
Question You are given an array shelf of n distinct integers that is a permutation of 1…n. Starting with target = 1, you repeatedly scan shelf from le...
Compute maximum distinct-product pickup days
Question Given an array of positive integers representing quantities of different products, on day i (starting from 1) you must pick exactly i distinc...
Determine blockage and parse HTML tokens
Question Given a set of 2-D circular stones, determine whether they can completely block the width of a river. You may define the input format. Given ...
Find most frequent log user
Question You are given a list of log entries in string format, where each entry contains a username and an access timestamp separated by a delimiter (...
Parse strings and find meeting slots
Question Given a text file where each line contains raw information, extract the user identifier and the numeric quantity on that line and store the r...
Implement string-path file system operations
Question LeetCode 1166. Design File System – extended to support Create(path, value), Get(path), Set(path, value) and Delete(path) with validation rul...
Implement matrix-indexing and expression resolver
Question Given a text file path whose contents include a single block starting with a line like "[2,4]" followed by rows of equal-length characters (e...
Evaluate dependent variable expressions
Question Given a target variable name and a list of assignment strings of the form 'Ti = expression' where the expression is either a number, a single...
Determine equality after limited swaps
Question LeetCode 1790. Check if One String Swap Can Make Strings Equal Follow-up: Given two strings, determine if they can become anagrams of each ot...