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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"Literally just signed a $600k offer. I only had 2 weeks to prep, so I focused entirely on the company-tagged lists here. If you're targeting L5+, don't overthink it."
"Coaches and bootcamp prep courses cost around $200-300 but PracHub Premium is actually less than a Netflix subscription. And it landed me a $178K offer."
"I honestly don't know how you guys gather so many real interview questions. It's almost scary. I walked into my Amazon loop and recognized 3 out of 4 problems from your database."
"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 np.random.choice
Implement a function similar to numpy.random.choice. Function signature choice(a, size=None, replace=True, p=None) -> samples Requirements - a can be:...
Maximize Letters from Disjoint Words
You are given an array words of lowercase English strings. Choose a subset of words such that: - each chosen word contains no repeated letter within i...
Check connectivity between two subway stations
You are given a description of subway stations A, B, C, D, E, ... as a graph. For each station, you are told which other stations it directly connects...
Solve array and tree algorithm challenges
Solve the following three algorithmic tasks: 1) Unique triplet sum: Given an integer array nums and an integer target (default 0), return all unique t...
Compute currency conversion via graph search
Given a list of currency pairs, e.g., [('USD','CAD'), ('CAD','EUR'), ...], and a parallel list of conversion ratios [1.1, 1.2, ...] where ratio r mean...
Find longest palindromic substring
Given a string s, return the longest contiguous substring of s that is a palindrome. Input - A single string s. Output - A string representing the lon...
Solve server updates and grid inconvenience minimization
1) You are given an integer array server of length n, where server[i] is the number of requests the i-th server can process. Over multiple days, you r...
Reverse sublist between equal-value nodes
Given the head of a singly linked list and a target value v that appears at least twice, reverse the sublist starting at the first node with value v a...
Transform tree using counterpart subtree sums
Given the roots of two complete binary trees with identical structure, modify the node values of the second tree so that each node equals the sum of a...
Compute intersections for each segment
You are given $n$ segments on a number line. Segment $i$ is the closed interval $[\text{startsAt}[i], \text{endsAt}[i]]$ (inclusive endpoints), with $...
Sort by squares and find k-th smallest
Given a nondecreasing sorted array of integers nums, do the following: 1) Reorder the original elements by increasing square value (equivalently, by a...
Explain data structure fundamentals
Explain how a hash map works internally: hashing, collision resolution strategies (separate chaining vs. open addressing), load factor, and resizing. ...
Implement and analyze number-pattern function
Implement a function print_number_lines(n) that prints n lines, where the i-th line contains the integers from 1 to i separated by spaces (e.g., n=3 p...
Implement bounds, minimum, pathfinding, and moving average
Solve the following data-structures problems: ( 1) Given two sorted integer lists A and B, merge them into a single non-decreasing array. Then, for a ...
Validate palindrome with constraints
Given a string s, return true if s reads the same forward and backward after removing all non-alphanumeric characters and ignoring letter case. Implem...
Count subarrays with at least k fruit pairs
Given an integer array nums where each value denotes a fruit type, and an integer k: For any subarray, define a 'pair' for fruit value v if its freque...
Implement KV store serialization
Implement serialization and deserialization for an in‑memory key‑value store to and from a contiguous bytes buffer. Keys are UTF‑8 strings; values may...
Minimize moves to transform floor layouts
You are given an initial arrangement of apartments across Floors 1–4 and a target arrangement. In one move you may reposition a single apartment to a ...
Approach verbose data-structure design
For a data-structure design problem whose behavior is easy to understand but whose implementation is lengthy, describe your step-by-step approach: cla...
Design and implement a bank account system
Design and implement a minimal banking service with the following capabilities: 1) Create bank accounts with unique IDs and an initial balance; suppor...