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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"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."
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Compute max island with constrained flips
Given an n×n binary grid G where 1=land and 0=water with 4-directional connectivity, return the size of the largest island achievable by flipping at m...
Debug and test a Python function in venv
Consider the Python snippet below. """ import math def accumulate(nums, start=0, cache={}): total = start for n in nums: if n % 2 == 0: nums.appen...
Implement and extend My Calendar III
Design and implement a booking system like LeetCode 732 (My Calendar III). Provide a class with methods: book(start, end) using half-open intervals [s...
Implement weighted sampling without replacement
Implement in Python a function sample_k(items, weights, k) that returns k items without replacement with probability proportional to weight. Requireme...
Find list pair with maximum overlap
You are given N labeled lists of items as a Python dict mapping list_name -> iterable of strings. Example input: {'L1': ['A','B','C'], 'L2': ['A','C',...
Implement randomized Quickselect without k-shift bug
Implement randomized Quickselect to return the k-th largest element (1-based k, 1 ≤ k ≤ n) from an unsorted integer array. Use an in-place partition t...
Compute binary-tree diameter via return-only DFS
Given the root of a binary tree, compute its diameter defined as the number of edges on the longest path between any two nodes. Implement a DFS that r...
Compute 95th-percentile call concurrency
Given N call sessions as half-open intervals [start, end) in UNIX seconds, design an algorithm to compute the 95th percentile of per-minute concurrent...
Solve subset-count and kth-factor problems
Two Independent Tasks A) Maximum Count Under Sum Constraint You are given an integer array arr and an integer budget n. Return the maximum number of e...
Solve and optimize 3Sum and variants at scale
Implement a function that returns all unique triplets (i, j, k) of indices whose values sum to a target T, with strong performance and deduplication g...
Implement sqrt with Newton vs binary search
Implement numerically robust square-root routines and analyze convergence Task 1 — sqrt_newton(x, tol=1e-12) Implement a Python function that returns ...
Implement fast sampling for weighted k-sided die
You must sample from a categorical distribution over k outcomes with probabilities p1..pk (sum to 1) without using built-in categorical samplers. You ...
Compute and Rank by Jaccard Similarity
Implement two functions: (1) jaccard_similarity(s1, s2) that tokenizes by splitting on any non-alphanumeric character, lowercases, treats tokens as se...
Implement blocked time-series cross-validation
Implement a panel-aware blocked time-series cross-validation splitter with an embargo. Input: DataFrame columns [loan_id, msa, month]. Requirements: (...
Implement list overlap and dense-ranked word frequencies
Part A — Multiset overlap count Implement count_overlap(a: List[int], b: List[int]) -> int that returns the size of the multiset intersection of a and...
Compute maximum concurrent trips from intervals
You’re given n trip intervals [start, end) in seconds, where start < end, representing when a rider’s trip starts and ends in a city on a specific day...
Implement sliding-window device anomaly
Streaming detection algorithm: Implement a function process_logins(stream) that consumes a time-ordered stream of login events (user_id, ts, device_id...
Implement lower_bound on unknown-size sorted array
Lower Bound in Unknown-Length Nondecreasing Array via API Setup You are given a non-decreasing integer array A of unknown length n. You cannot access ...
Implement minimum window substring with counts
Implement min_window_with_counts(s, t) Task Write a function: - min_window_with_counts(s: str, t: str) -> tuple[int, int] that returns the inclusive (...
Compute average unique pins per user
Task: Average Unique Pins Per User You are given a mapping from user IDs to their lists of pin IDs. Implement a function that computes the mean number...