Exam prep · Coding interview

Coding interview flashcards for data structures and algorithms

Interview problems are solved by recognizing a pattern, not by remembering a solution. Flashcards are the fastest way to build that recognition: pattern on the front, the signal that it applies on the back. Start with the decks below, then card every problem you solve.

Updated 2026-10-23. Decks are shared by Quizcard and its users; study them on the page or copy them into a free account.

Coding interview at a glance

What the Coding interview tests

• Arrays and strings. Two pointers, sliding window, prefix sums, in-place operations.
• Hash maps and sets. Counting, lookups, grouping, deduplication. The most common “trick” in easy and medium problems.
• Linked lists, stacks, queues. Reversal, cycle detection, monotonic stacks, BFS with a queue.
• Trees and graphs. DFS and BFS, binary search trees, tries, topological sort, union-find, shortest paths.
• Heaps and sorting. Top-k problems, merge k lists, interval scheduling, custom comparators.
• Binary search. On sorted arrays and on the answer space.
• Dynamic programming. 1-D and 2-D tables, knapsack, longest common subsequence, memoization versus tabulation.
• Big-O. Time and space of every structure’s operations, and of the standard algorithms.
• System design (senior roles). Load balancing, caching, databases, queues, consistency trade-offs.

Free Coding interview flashcard decks

• Intro to Programming and Data Structures30 cards · University · Algorithms · Basics · Complexity · Data structures
• Discrete Mathematics: Logic, Sets, and Counting30 cards · University · Counting · Functions · Graphs · Logic
• Computer Networks: Fundamentals30 cards · University · Application · Models · Network · Performance
• Coding Interview Patterns: Arrays, Hash Maps, Two Pointers and Sliding Window39 cards · University · Binary Search Variants · Cyclic Sort · Fast & Slow Pointers · Hash Map / Set Tricks

Missing a topic? Upload the chapter from your prep book and Quizcard builds the deck for you, grouped by topic, with figures kept from PDFs. How it works.

Test yourself: free Coding interview practice quizzes

• Intro to Programming and Data Structures quiz18 multiple-choice questions with explanations · no account needed
• Coding Interview Patterns: Arrays, Hash Maps, Two Pointers and Sliding Window quiz11 multiple-choice questions with explanations · no account needed

Each quiz scores you at the end and explains every answer. Redo it any time; the questions reshuffle.

Sample cards from “Intro to Programming and Data Structures”

What is a binary search tree?

Answer: A binary tree where each node's left subtree holds smaller keys and right subtree holds larger keys.

Explanation

Search is O(log n) when balanced, O(n) when degenerate.

What is version control and what does Git's commit do?

Answer: Version control tracks changes to code over time; a commit records a snapshot with a message.

Explanation

Branches let you work on features without affecting main.

What is a unit test?

Answer: A small automated test that checks one function or component in isolation.

Explanation

Fast feedback; catches regressions.

What is polymorphism?

Answer: The ability for different classes to respond to the same method call in their own way.

Explanation

Example: shape.area() works for Circle and Square.

What is encapsulation?

Answer: Bundling data with the methods that operate on it and restricting direct access to internal state.

Explanation

Achieved with private fields and public methods.

What is inheritance?

Answer: A mechanism where a class (subclass) acquires the attributes and methods of another class (superclass).

Explanation

Supports code reuse and 'is-a' relationships.

Showing 6 of 30 cards. Study the whole deck or copy it into your account.

A flashcard study plan for the Coding interview

1. Week 1: foundations. Study the data structures and Big-O decks until the complexity table is automatic. Card the operations of every structure.
2. Weeks 2 to 3: patterns. Solve two problems a day by category. After each, make one card: the problem’s signal on the front (“find pairs summing to k”), the pattern and complexity on the back (“hash map, O(n)”).
3. Weeks 4 to 5: mixed practice under a 40-minute timer. Card every problem you could not solve or solved slowly.
4. Week 6: mock interviews out loud. Review the missed deck daily; talk through the cards as if explaining to an interviewer.

How to write Coding interview cards that work

• Never card a full solution. Card the recognition cue and the first step; the rest should come from understanding.
• Make a card for each classic pitfall: integer overflow, off-by-one in binary search, modifying a list while iterating, mutable default arguments.
• Complexity cards should pair a structure with an operation: “hash map insert, average and worst case?”
• Paste your notes or a chapter of a prep book into Quizcard and generate a deck; then prune it to the cards you actually get wrong.

Questions

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