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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"10 years of experience but never worked at a top company. PracHub's senior-level questions helped me break into FAANG at 35. Age is just a number."
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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."
Compute probability of random arithmetic progression triple
You have the integers from 1 to 30 inclusive. You randomly choose 3 distinct numbers without replacement, and all 3-element subsets are equally likely...
Implement a basic pivot table with totals
You are given a small in-memory table of data and are asked to implement a simplified pivot table operation and a printer for it. Assume the input dat...
Find lowest common ancestor in tree
You are given the root of a binary search tree (BST) and two distinct nodes p and q that are guaranteed to exist in the tree. Task (BST case): - Find ...
Solve tree diameter and grid path problems
You are interviewing for a software engineer / ML intern role and are given the following algorithmic problems. --- Question 1: Longest Path in a Tree...
Implement decoder-only GPT-style transformer
Goal Implement a simplified decoder-only Transformer language model (similar in spirit to GPT) for next-token prediction. The implementation should be...
Design LFU cache with distributed extension
Problem You are asked to design and implement a data structure that behaves like an in-memory cache with a Least Frequently Used (LFU) eviction policy...
Count integer pairs satisfying 1/x + 1/y = 1/N
You are given a positive integer N (\(1 \le N \le 10^6\)). Consider the Diophantine equation: \[ \frac{1}{x} + \frac{1}{y} = \frac{1}{N}, \] where x a...
Maximize stock profit with one or two trades
You are given an array prices where prices[i] is the price of a given stock on day i (0-indexed). You want to maximize your profit by choosing when to...
Find mode in a trinary search tree
You are given the root of a trinary search tree where each node has up to three children: `text class Node { int val; Node left; // all values ...
Implement most_frequent_key without using max()
Problem (Python OOP) You are given two classes. Parent precomputes frequency counts of items (as strings) from an input list. `python class Parent: ...
Implement Univariate Linear Regression with Ordinary Least Squares
Implement univariate (simple) linear regression fitted in batch with the ordinary least squares (OLS) closed-form solution. You must implement the for...
Maximum-Product Simple Path in a Complete Directed Graph
You are given a complete directed graph with n nodes labeled 0 through n - 1. For every ordered pair of distinct nodes (i, j), there is a directed edg...
Count Distinct Island Shapes in a Binary Grid
You are given an m x n binary grid grid, where grid[i][j] is either 0 (water) or 1 (land). An island is a maximal group of 1-cells connected 4-directi...
Compute last-5-minute QPS in memory
Problem You are building a lightweight in-memory component that tracks the query load (QPS) of a service. Design a data structure with two operations:...
Compute triangle min path and dice stopping stats
You are given two independent interview questions. 1) Triangle minimum path sum (DP) Given a triangular array triangle with n rows, find the minimum p...
Find longest subsequence of x that is a substring of y
Given two strings x and y, compute the maximum length of a string s such that: - s is a subsequence of x (can delete zero or more characters from x wi...
Remove duplicates from a singly linked list
You are given the head of a singly linked list of integers. Modify the list in place so that it contains only the first occurrence of each value (i.e....
Guide a mouse to find cheese with APIs
This question evaluates the ability to reason about graph exploration and stateful API interaction in an unknown 2D grid, assessing competencies in se...
Rotate a Matrix In Place
Given an n x n matrix of integers, rotate the matrix 90 degrees clockwise. Implement the function in Python. You may use a straightforward approach wi...
Implement three interview-style coding tasks
You are given three separate coding tasks, all focused on algorithm and data-structure design. --- Task 1: Longest Bounded-Difference Subarray You are...