Project 3: Dynamic Data Structures Library
Implement core linear data structures with strict invariants and memory discipline.
Quick Reference
| Attribute | Value |
|---|---|
| Difficulty | Intermediate |
| Time Estimate | 2 weeks |
| Language | C |
| Prerequisites | Pointers, malloc/free |
| Key Topics | stacks, queues, lists, invariants |
1. Learning Objectives
By completing this project, you will:
- Implement stacks, queues, deques, and linked lists from first principles.
- Define and enforce invariants for each structure.
- Handle allocation failures without corrupting state.
- Build a reusable API with tests.
2. Theoretical Foundation
2.1 Core Concepts
- Linear structures: State changes are local and must preserve links.
- Invariants: Head/tail consistency and size correctness.
- Ownership: Clear rules for allocation and freeing.
2.2 Why This Matters
TAOCP uses these structures as building blocks. A single pointer bug corrupts every dependent algorithm.
2.3 Historical Context / Background
These structures predate modern languages and remain the backbone of low-level systems code.
2.4 Common Misconceptions
- “Size can be recomputed later”: It should be tracked correctly.
- “NULL checks are enough”: You must also ensure correct link topology.
3. Project Specification
3.1 What You Will Build
A C library implementing stack, queue, deque, singly linked list, and doubly linked list, with iterator support.
3.2 Functional Requirements
- Stack: push, pop, peek, size.
- Queue: enqueue, dequeue, front, size.
- List: insert, remove, find, iterate.
- Deque: push/pop both ends.
3.3 Non-Functional Requirements
- Reliability: All operations leave structure valid.
- Performance: O(1) for head/tail operations.
- Usability: Clear error codes and docs.
3.4 Example Usage / Output
stack_push(10)
stack_pop() -> 10
queue_enqueue(5)
queue_dequeue() -> 5
3.5 Real World Outcome
You will have a small library that can be reused in later TAOCP projects without reimplementation.
4. Solution Architecture
4.1 High-Level Design
┌──────────────┐ ┌──────────────┐ ┌──────────────┐
│ public API │────▶│ structure impl│────▶│ tests │
└──────────────┘ └──────────────┘ └──────────────┘
4.2 Key Components
| Component | Responsibility | Key Decisions |
|---|---|---|
| Stack | LIFO behavior | Array vs list |
| Queue/Deque | FIFO and double-ended | Tail pointer |
| List | Insert/remove | Singly vs doubly |
4.3 Data Structures
typedef struct Node {
int value;
struct Node *next;
struct Node *prev;
} Node;
4.4 Algorithm Overview
Key Algorithm: List insert
- Allocate node.
- Fix next/prev pointers.
- Update head/tail and size.
Complexity Analysis:
- Time: O(1) for head/tail ops, O(n) for search.
- Space: O(n) for n elements.
5. Implementation Guide
5.1 Development Environment Setup
gcc --version
5.2 Project Structure
project-root/
├── include/ds.h
├── src/ds.c
├── tests/
└── Makefile
5.3 The Core Question You’re Answering
“Which invariants must always be true after any operation?”
5.4 Concepts You Must Understand First
- Pointer ownership and freeing.
- Sentinel nodes vs NULL end markers.
- Error propagation in C.
5.5 Questions to Guide Your Design
- How do you detect and handle allocation failure?
- What is the invariant for head/tail pointers?
- How do you ensure size stays correct?
5.6 Thinking Exercise
Write assertions that validate a doubly linked list after each mutation.
5.7 The Interview Questions They’ll Ask
- What invariants define a correct linked list?
- Why might a deque be more efficient than a list?
- How do you avoid memory leaks on error paths?
5.8 Hints in Layers
Hint 1: Implement stack using a dynamic array first. Hint 2: Add queue with head/tail pointers. Hint 3: Add doubly linked list with prev pointers.
5.9 Books That Will Help
| Topic | Book | Chapter |
|---|---|---|
| Lists | TAOCP Vol 1 | Ch. 2 |
| C memory | Effective C | memory chapters |
5.10 Implementation Phases
Phase 1: Foundation (3-4 days)
- Stack and queue implementations.
Phase 2: Core Functionality (4-5 days)
- Deque and linked lists.
Phase 3: Polish & Edge Cases (2-3 days)
- Iterators, tests, and invariants.
5.11 Key Implementation Decisions
| Decision | Options | Recommendation | Rationale |
|---|---|---|---|
| Stack backing | array vs list | array | cache-friendly |
| List type | singly vs doubly | doubly | easier removal |
6. Testing Strategy
6.1 Test Categories
| Category | Purpose | Examples |
|---|---|---|
| Basic ops | Correct behavior | push/pop order |
| Edge cases | Empty structures | pop on empty |
| Invariants | Structure validity | link checks |
6.2 Critical Test Cases
- Push then pop yields original value.
- Queue preserves FIFO order.
- List removal preserves connectivity.
6.3 Test Data
Small sequences of integers
7. Common Pitfalls & Debugging
7.1 Frequent Mistakes
| Pitfall | Symptom | Solution |
|---|---|---|
| Lost node | Leak | Track ownership |
| Broken links | Crash | Validate pointers |
| Wrong size | Incorrect API behavior | Update size on all paths |
7.2 Debugging Strategies
- Add invariant checks in debug builds.
- Use valgrind for leaks.
7.3 Performance Traps
Repeated scans for tail access; keep tail pointer.
8. Extensions & Challenges
8.1 Beginner Extensions
- Add list iterator API.
8.2 Intermediate Extensions
- Add freelist allocator for nodes.
8.3 Advanced Extensions
- Add thread-safe variants.
9. Real-World Connections
- OS schedulers, buffers, and queues rely on these structures.
10. Resources
- TAOCP Vol 1 Chapter 2
- Effective C
11. Self-Assessment Checklist
- I can state the invariants for each structure.
- All tests pass without leaks.
12. Submission / Completion Criteria
Minimum: Stack and queue correct. Full: All structures with tests. Excellence: Custom allocator and iterators.
This guide was generated from LEARN_TAOCP_DEEP_DIVE.md. For the complete learning path, see the parent directory README.