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LeetCode Prep

The Curriculum

Every chapter, ordered from foundations to advanced. Prerequisites guide the path — master the basics and the harder patterns unlock.

Data Structures

1

Arrays & Hashing

The foundation: indexing, hash maps, and frequency counting.

Hashing & Frequency Maps

Use hash maps/sets for O(1) lookups, deduplication, and counting.

18 problems (3 quiz · 15 code)
Prefix Sums

Precompute running sums to answer range queries in O(1).

Prereqs: Hashing & Frequency Maps

7 problems (2 quiz · 5 code)
2

Strings

String manipulation, parsing, and encoding.

String Manipulation

Iterate, build, and transform strings efficiently.

16 problems (2 quiz · 14 code)
Anagrams & Encoding

Group, compare, and encode strings using canonical keys.

Prereqs: Hashing & Frequency Maps

7 problems (2 quiz · 5 code)
3

Stacks & Queues

LIFO/FIFO structures, monotonic stacks, and deques.

Stacks & Monotonic Stack

Use a stack for matching, parsing, and next-greater-element problems.

16 problems (2 quiz · 14 code)
Queues & Deques

Use FIFO queues and double-ended queues for windows and BFS.

Prereqs: Stacks & Monotonic Stack

5 problems (2 quiz · 3 code)
4

Linked Lists

Pointer manipulation, reversal, and cycle detection.

Traversal & Reversal

Walk, build, and reverse singly linked lists with pointers.

9 problems (2 quiz · 7 code)
Fast & Slow Pointers

Detect cycles and find midpoints with two-speed pointers.

Prereqs: Traversal & Reversal

7 problems (2 quiz · 5 code)
5

Trees & BSTs

Binary tree traversal, recursion on trees, and search trees.

Tree Traversals (DFS/BFS)

Traverse binary trees recursively and level-by-level.

Prereqs: Traversal & Reversal

17 problems (3 quiz · 14 code)
Binary Search Trees

Exploit BST ordering for search, insertion, and validation.

Prereqs: Tree Traversals (DFS/BFS)

6 problems (2 quiz · 4 code)
6

Heaps & Priority Queues

Top-K, streaming medians, and scheduling with heaps.

Heaps & Top-K

Use heaps for top-K, k-way merges, and streaming order statistics.

Prereqs: Tree Traversals (DFS/BFS)

14 problems (3 quiz · 11 code)
7

Tries

Prefix trees for fast string lookups and autocomplete.

Tries & Prefix Trees

Build prefix trees for fast word and prefix queries.

Prereqs: Tree Traversals (DFS/BFS), String Manipulation

6 problems (2 quiz · 4 code)
8

Graphs

Graph representation, traversal, and connectivity.

Graph Representation & Traversal

Model graphs as adjacency lists/matrices and traverse them.

Prereqs: Tree Traversals (DFS/BFS)

7 problems (2 quiz · 5 code)
Union-Find (Disjoint Set)

Track connectivity with union by rank and path compression.

Prereqs: Graph Representation & Traversal

5 problems (2 quiz · 3 code)

Algorithms

1

Two Pointers & Sliding Window

Linear-scan patterns for pairs, subarrays, and substrings.

Two Pointers

Converge pointers to solve pair, palindrome, and partition problems.

Prereqs: Hashing & Frequency Maps

16 problems (2 quiz · 14 code)
Sliding Window

Maintain a moving window to optimize subarray/substring scans.

Prereqs: Two Pointers

14 problems (3 quiz · 11 code)
2

Binary Search

Searching sorted data and binary searching the answer space.

Binary Search on Arrays

Halve the search space on sorted (and rotated) arrays.

Prereqs: Hashing & Frequency Maps

16 problems (2 quiz · 14 code)
Binary Search on the Answer

Binary search a monotonic feasibility function over a value range.

Prereqs: Binary Search on Arrays

6 problems (2 quiz · 4 code)
3

Recursion & Backtracking

Recursive enumeration of subsets, permutations, and combinations.

Recursion Fundamentals

Define base cases and recursive cases that shrink the problem.

7 problems (2 quiz · 5 code)
Backtracking

Explore choices with prune-and-undo over subsets and permutations.

Prereqs: Recursion Fundamentals

17 problems (3 quiz · 14 code)
4

Greedy

Locally optimal choices that yield a global optimum.

Greedy Algorithms

Prove and apply a greedy choice that stays globally optimal.

11 problems (2 quiz · 9 code)
5

Dynamic Programming

Overlapping subproblems, memoization, and tabulation.

1-D Dynamic Programming

Define a state and recurrence over a single dimension.

Prereqs: Recursion Fundamentals

19 problems (3 quiz · 16 code)
2-D Dynamic Programming

Grid and two-sequence DP (edit distance, LCS, unique paths).

Prereqs: 1-D Dynamic Programming

10 problems (2 quiz · 8 code)
Knapsack & Subset DP

Choose items under a capacity/target constraint.

Prereqs: 1-D Dynamic Programming

5 problems (2 quiz · 3 code)
6

Graph Algorithms

BFS/DFS patterns, topological sort, and shortest paths.

BFS & DFS Patterns

Flood fill, connected components, and shortest unweighted paths.

Prereqs: Graph Representation & Traversal

11 problems (2 quiz · 9 code)
Topological Sort

Order a DAG and detect cycles (course scheduling).

Prereqs: BFS & DFS Patterns

7 problems (2 quiz · 5 code)
Shortest Paths

Dijkstra for weighted graphs and BFS for unweighted ones.

Prereqs: BFS & DFS Patterns

7 problems (2 quiz · 5 code)
7

Intervals

Merging, scheduling, and sweeping over intervals.

Interval Merging & Scheduling

Sort and sweep intervals to merge, insert, and detect overlaps.

Prereqs: Greedy Algorithms

7 problems (2 quiz · 5 code)
8

Bit Manipulation & Math

Bitwise tricks, number theory, and math-heavy problems.

Bit Manipulation

Use XOR, masks, and shifts for O(1)-space tricks.

12 problems (2 quiz · 10 code)
Math & Number Theory

GCD, primes, modular arithmetic, and overflow-safe math.

11 problems (2 quiz · 9 code)

System Design

1

System Design Fundamentals

Scalability, latency vs throughput, load balancing, and caching.

Scalability & Performance

Reason about latency vs throughput and scale up vs scale out.

2 problems
Load Balancing & Proxies

Distribute traffic with load balancers, reverse proxies, and health checks.

Prereqs: Scalability & Performance

2 problems
Caching & CDNs

Add caches and CDNs with the right write/eviction policy.

Prereqs: Scalability & Performance

3 problems
2

Data Storage & Scaling

Choosing data stores, sharding, replication, and indexing.

SQL vs NoSQL & Data Modeling

Match the data store and schema to access patterns.

Prereqs: Scalability & Performance

2 problems
Partitioning & Replication

Shard for scale and replicate for availability and reads.

Prereqs: SQL vs NoSQL & Data Modeling

2 problems
Indexing & Query Performance

Speed reads with the right indexes and understand their cost.

Prereqs: SQL vs NoSQL & Data Modeling

1 problems
3

Distributed Systems

CAP & consistency, messaging, idempotency, and rate limiting.

CAP & Consistency Models

Trade consistency, availability, and partition tolerance.

Prereqs: Partitioning & Replication

2 problems
Message Queues & Async Processing

Decouple services with queues, pub/sub, and streams.

Prereqs: Scalability & Performance

2 problems
Resilience & Rate Limiting

Stay correct under failure with idempotency, retries, and rate limits.

Prereqs: Message Queues & Async Processing

2 problems
4

Cloud System Design

Cloud building blocks, autoscaling, serverless, reliability, and cost.

Cloud Building Blocks

Compose compute, object storage, managed databases, and networking.

Prereqs: Scalability & Performance

3 problems
Autoscaling & Multi-Region

Scale elastically and survive zone/region failure in the cloud.

Prereqs: Load Balancing & Proxies, Cloud Building Blocks

2 problems
Serverless & Event-Driven Cloud

Build event-driven systems with functions, managed queues, and streams.

Prereqs: Cloud Building Blocks, Message Queues & Async Processing

2 problems
Reliability, Observability & Cost

Operate cloud systems with SLOs, monitoring, and cost control.

Prereqs: Cloud Building Blocks

2 problems
5

Design Case Studies

Driving an end-to-end design interview on real products.

End-to-End Design Cases

Drive a design interview from requirements to a scaled architecture.

Prereqs: Caching & CDNs, Partitioning & Replication, Cloud Building Blocks

2 problems