harivansh-afk/veet-code
1
0
Fork 0
mirror of https://github.com/harivansh-afk/veet-code.git synced 2026-04-15 05:02:12 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

update generate files and problem examples to be consistent

Browse source
This commit is contained in:
Harivansh Rathi 2025-12-14 16:03:56 -05:00
parent 186bb75289
commit 933b466c25
2 changed files with 342 additions and 255 deletions
Download patch file Download diff file Expand all files Collapse all files

234
.claude/commands/generate.md
View file

@ -1,83 +1,54 @@
---
description: Generate a new practice problem with tests
argument-hint: [difficulty] [topic]
allowed-tools: Write, Bash(mkdir:*)
allowed-tools: Write, Bash(mkdir:*), Bash(cd:*), Bash(python:*), Bash(rm:*)
---
# Generate a New Practice Problem
**Reference**: @.claude/problem-examples.md for consistent formatting and quality examples.
You are generating a practical implementation problem for veetcode - a terminal-based coding practice tool.
You are generating a practical implementation problem for veetcode.
## Arguments Provided
- Difficulty: $1 (if empty, ask user to choose: easy, medium, or hard)
- Topic: $2 (if empty, ask user what concept/topic they want to practice)
## Problem Style Guide
## Generation Workflow
Generate **practical implementation** problems, NOT abstract LeetCode puzzles:
### Step 1: Gather Requirements
If arguments not provided, ask user:
1. Difficulty: easy, medium, or hard
2. Topic/concept they want to practice
3. Confirm with a one-line problem summary before proceeding
### DO:
- Use real-world business context (e.g., "You are building a payment system...")
- Provide clear function signatures with type hints
- Include 2-3 concrete examples with explanations
- List explicit constraints
- Focus on practical skills: data transformation, validation, API-like operations
### Step 2: Design the Problem (in your head)
Before writing any files, mentally design:
- The problem scenario (real-world context)
- Function signature with types
- The ACTUAL SOLUTION (keep this secret - never write to files)
- Test cases that verify the solution
- Edge cases
### DON'T:
- Create pure algorithmic puzzles without context
- Use abstract mathematical framing
- Make problems that feel like textbook exercises
## Difficulty Calibration
**Easy** (15-25 min):
- Single data structure (list, dict, set)
- 1-2 core concepts
- 3-4 test cases
- ~20-30 lines solution
**Medium** (30-40 min):
- Multiple data structures
- 3-4 concepts (sorting, hash maps, two pointers)
- 5-6 test cases including edge cases
- ~40-60 lines solution
**Hard** (45-60 min):
- Custom classes or complex data structures
- 5+ concepts (DP, graphs, sliding window + state)
- 7-10 test cases with tricky edge cases
- ~80+ lines solution
## Output Format
### 1. First, confirm with the user:
- The difficulty level
- The topic/concept
- A one-line problem summary
### 2. Generate the problem name
Create a kebab-case name (e.g., `validate-transactions`, `rate-limiter`, `word-frequency`)
### 3. Create the directory
### Step 3: Create Directory
```bash
mkdir -p problems/{difficulty}/{problem-name}
```
### 4. Create solution.py
### Step 4: Write solution.py (SKELETON ONLY)
Write ONLY the skeleton - never include the solution!
Structure:
```python
"""
{Problem Title}
{Story-based description in 2-3 sentences with real-world context}
{Story-based description in 2-3 sentences with real-world context.
Frame it as a real task: "You're building...", "Your team needs...", etc.}
Example 1:
Input: {param1} = {value1}, {param2} = {value2}
Output: {expected}
Explanation: {why this is the answer}
Explanation: {brief explanation}
Example 2:
Input: {param1} = {value1}, {param2} = {value2}
@ -90,59 +61,148 @@ Constraints:
"""
def {function_name}({params_with_types}) -> {return_type}:
"""{One-line docstring describing what to return}."""
def {function_name}({params}: {types}) -> {return_type}:
"""{One-line description of what to return}."""
pass # Your implementation here
```
### 5. Create tests.py
### Step 5: Write tests.py (CONSISTENT FORMAT)
Follow this EXACT format for all tests:
Structure:
```python
"""Tests for {problem_name}."""
import pytest
from solution import {function_name}
def test_basic_case():
"""Test the example from the problem description."""
assert {function_name}(...) == ...
class TestBasicCases:
"""Test basic functionality with typical inputs."""
def test_example_one(self):
"""Test first example from problem description."""
assert {function_name}(...) == ...
def test_example_two(self):
"""Test second example from problem description."""
assert {function_name}(...) == ...
def test_typical_case(self):
"""Test another common case."""
assert {function_name}(...) == ...
def test_another_case():
"""Test another typical case."""
assert {function_name}(...) == ...
class TestEdgeCases:
"""Test edge cases and boundary conditions."""
def test_empty_input(self):
"""Test with empty or minimal input."""
assert {function_name}(...) == ...
def test_single_element(self):
"""Test with single element input."""
assert {function_name}(...) == ...
def test_boundary_values(self):
"""Test boundary conditions."""
assert {function_name}(...) == ...
def test_edge_case_empty():
"""Test empty or minimal input."""
assert {function_name}(...) == ...
def test_edge_case_boundary():
"""Test boundary conditions."""
assert {function_name}(...) == ...
# Add more tests based on difficulty:
# Easy: 3-4 tests
# Medium: 5-6 tests
# Hard: 7-10 tests
# Test count by difficulty:
# Easy: 4-5 tests (2 basic, 2-3 edge)
# Medium: 6-8 tests (3 basic, 3-5 edge)
# Hard: 8-12 tests (4 basic, 4-8 edge)
```
## Example Problems by Topic
### Step 6: VERIFY TESTS WORK (CRITICAL)
**Arrays/Lists**: frequency counting, deduplication, sliding window, two pointers
**Strings**: parsing, validation, transformation, pattern matching
**Hash Maps**: grouping, caching, lookup optimization
**Trees/Graphs**: traversal, path finding, hierarchy operations
**OOP Design**: class design, state management, encapsulation
**Data Processing**: ETL operations, aggregation, filtering pipelines
You MUST verify the tests are solvable before telling the user. Run this verification using inline Python - DO NOT write the solution to any file:
## After Generation
```bash
cd problems/{difficulty}/{problem-name} && python -c "
import sys
from types import ModuleType
Tell the user:
1. The path to their new problem: `problems/{difficulty}/{problem-name}/`
2. How to start practicing: `uv run veetcode` then select the problem
3. The file to edit: `solution.py`
# Define the actual solution INLINE (user cannot see this)
def {function_name}({params}):
# YOUR SOLUTION HERE - implement it fully
...
Now, let's generate a problem! If difficulty or topic weren't provided, ask the user to choose.
# Create a fake 'solution' module
solution_module = ModuleType('solution')
solution_module.{function_name} = {function_name}
sys.modules['solution'] = solution_module
# Run pytest
import pytest
exit_code = pytest.main(['tests.py', '-v'])
sys.exit(exit_code)
"
```
If tests FAIL:
- Fix the tests (not the solution approach)
- Re-run verification
- Do NOT proceed until all tests pass
If tests PASS:
- Proceed to tell user the problem is ready
### Step 7: Confirm to User
Only after verification passes, tell the user:
```
✅ Problem created and verified!
📁 Location: problems/{difficulty}/{problem-name}/
📝 Edit: solution.py
🚀 Run: uv run veetcode → select "{problem-name}"
Good luck!
```
## Problem Style Guide
### DO:
- Real-world business context ("You're building a payment API...")
- Clear function signatures with type hints
- 2-3 concrete examples with explanations
- Explicit constraints
- Practical skills: data transformation, validation, business logic
### DON'T:
- Abstract algorithmic puzzles without context
- Mathematical framing ("Given an array of integers...")
- Textbook exercise style
- Overly complex for the difficulty level
## Difficulty Calibration
**Easy** (15-25 min):
- Single data structure (list, dict, set)
- 1-2 concepts
- 4-5 test cases
- ~20-30 line solution
**Medium** (30-40 min):
- Multiple data structures
- 3-4 concepts
- 6-8 test cases
- ~40-60 line solution
**Hard** (45-60 min):
- Custom classes or complex structures
- 5+ concepts
- 8-12 test cases
- ~80+ line solution
## Topic Ideas
- **Arrays**: frequency counting, deduplication, sliding window, two pointers
- **Strings**: parsing, validation, transformation, pattern matching
- **Hash Maps**: grouping, caching, lookup optimization, counting
- **Classes**: state management, encapsulation, business entities
- **Data Processing**: filtering, aggregation, transformation pipelines
Now, let's generate a problem! Ask for difficulty and topic if not provided.

363
.claude/problem-examples.md
View file

@ -2,6 +2,8 @@
Reference examples for generating consistent, high-quality practice problems.
---
## Easy Example: Email Validator
**solution.py**:
@ -9,15 +11,14 @@ Reference examples for generating consistent, high-quality practice problems.
"""
Email Validator
You're building a user registration system. Before storing emails in your
database, you need to validate that they follow the correct format.
Write a function that checks if an email address is valid.
You're building a user registration system for an e-commerce platform.
Before storing customer emails in your database, you need to validate
that they follow the correct format to prevent data quality issues.
Example 1:
Input: email = "user@example.com"
Output: True
Explanation: Has username, @, domain with dot
Explanation: Has username, single @, domain with dot
Example 2:
Input: email = "invalid-email"
@ -31,8 +32,8 @@ Example 3:
Constraints:
- Input is always a string
- Valid emails have: non-empty username, exactly one @, domain with at least one dot
- No spaces allowed anywhere in the email
- Valid: non-empty username, exactly one @, domain with at least one dot
- No spaces allowed anywhere
"""
@ -43,32 +44,45 @@ def is_valid_email(email: str) -> bool:
**tests.py**:
```python
"""Tests for email-validator."""
import pytest
from solution import is_valid_email
def test_valid_simple():
assert is_valid_email("user@example.com") == True
class TestBasicCases:
"""Test basic functionality with typical inputs."""
def test_valid_simple_email(self):
"""Test standard email format."""
assert is_valid_email("user@example.com") == True
def test_valid_with_subdomain(self):
"""Test email with subdomain."""
assert is_valid_email("user.name@mail.example.co.uk") == True
def test_invalid_missing_at(self):
"""Test email without @ symbol."""
assert is_valid_email("userexample.com") == False
def test_valid_with_dots():
assert is_valid_email("user.name@example.co.uk") == True
class TestEdgeCases:
"""Test edge cases and boundary conditions."""
def test_empty_string(self):
"""Test with empty input."""
assert is_valid_email("") == False
def test_invalid_no_at():
assert is_valid_email("userexample.com") == False
def test_empty_username(self):
"""Test with nothing before @."""
assert is_valid_email("@example.com") == False
def test_no_domain_dot(self):
"""Test domain without dot."""
assert is_valid_email("user@examplecom") == False
def test_invalid_no_domain_dot():
assert is_valid_email("user@examplecom") == False
def test_invalid_empty_username():
assert is_valid_email("@example.com") == False
def test_invalid_spaces():
assert is_valid_email("user @example.com") == False
def test_spaces_in_email(self):
"""Test email containing spaces."""
assert is_valid_email("user @example.com") == False
```
---
@ -80,11 +94,9 @@ def test_invalid_spaces():
"""
Transaction Grouper
You're building a financial dashboard. Users want to see their transactions
grouped by category, with totals calculated for each group.
Given a list of transactions (each with amount, category, and date),
return a dictionary grouping transactions by category with their total.
You're building a financial dashboard for a budgeting app. Users want
to see their spending grouped by category with totals, so they can
understand where their money is going each month.
Example 1:
Input: transactions = [
@ -101,67 +113,85 @@ Example 2:
Explanation: No transactions means empty result
Constraints:
- Each transaction has "amount" (positive int), "category" (string), "date" (string)
- Each transaction has "amount" (positive int), "category" (str), "date" (str)
- Categories are case-sensitive
- Return categories in any order
- Amount is always positive
"""
def group_transactions(transactions: list[dict]) -> dict[str, int]:
"""Return dictionary mapping category to total amount."""
"""Return dictionary mapping each category to its total amount."""
pass # Your implementation here
```
**tests.py**:
```python
"""Tests for group-transactions."""
import pytest
from solution import group_transactions
def test_multiple_categories():
txns = [
{"amount": 50, "category": "food", "date": "2024-01-01"},
{"amount": 30, "category": "food", "date": "2024-01-02"},
{"amount": 100, "category": "transport", "date": "2024-01-01"}
]
assert group_transactions(txns) == {"food": 80, "transport": 100}
class TestBasicCases:
"""Test basic functionality with typical inputs."""
def test_multiple_categories(self):
"""Test grouping across different categories."""
txns = [
{"amount": 50, "category": "food", "date": "2024-01-01"},
{"amount": 30, "category": "food", "date": "2024-01-02"},
{"amount": 100, "category": "transport", "date": "2024-01-01"}
]
assert group_transactions(txns) == {"food": 80, "transport": 100}
def test_single_category(self):
"""Test all transactions in one category."""
txns = [
{"amount": 10, "category": "food", "date": "2024-01-01"},
{"amount": 20, "category": "food", "date": "2024-01-02"},
{"amount": 30, "category": "food", "date": "2024-01-03"}
]
assert group_transactions(txns) == {"food": 60}
def test_single_transaction(self):
"""Test with just one transaction."""
txns = [{"amount": 25, "category": "entertainment", "date": "2024-01-01"}]
assert group_transactions(txns) == {"entertainment": 25}
def test_empty_list():
assert group_transactions([]) == {}
class TestEdgeCases:
"""Test edge cases and boundary conditions."""
def test_empty_list(self):
"""Test with no transactions."""
assert group_transactions([]) == {}
def test_single_transaction():
txns = [{"amount": 25, "category": "entertainment", "date": "2024-01-01"}]
assert group_transactions(txns) == {"entertainment": 25}
def test_case_sensitive_categories(self):
"""Test that categories are case-sensitive."""
txns = [
{"amount": 10, "category": "Food", "date": "2024-01-01"},
{"amount": 20, "category": "food", "date": "2024-01-02"}
]
result = group_transactions(txns)
assert result == {"Food": 10, "food": 20}
def test_many_categories(self):
"""Test with many different categories."""
txns = [
{"amount": 1, "category": "a", "date": "2024-01-01"},
{"amount": 2, "category": "b", "date": "2024-01-01"},
{"amount": 3, "category": "c", "date": "2024-01-01"},
{"amount": 4, "category": "d", "date": "2024-01-01"}
]
assert group_transactions(txns) == {"a": 1, "b": 2, "c": 3, "d": 4}
def test_single_category_multiple_transactions():
txns = [
{"amount": 10, "category": "food", "date": "2024-01-01"},
{"amount": 20, "category": "food", "date": "2024-01-02"},
{"amount": 30, "category": "food", "date": "2024-01-03"}
]
assert group_transactions(txns) == {"food": 60}
def test_case_sensitive_categories():
txns = [
{"amount": 10, "category": "Food", "date": "2024-01-01"},
{"amount": 20, "category": "food", "date": "2024-01-02"}
]
result = group_transactions(txns)
assert result == {"Food": 10, "food": 20}
def test_many_categories():
txns = [
{"amount": 1, "category": "a", "date": "2024-01-01"},
{"amount": 2, "category": "b", "date": "2024-01-01"},
{"amount": 3, "category": "c", "date": "2024-01-01"},
{"amount": 4, "category": "d", "date": "2024-01-01"}
]
assert group_transactions(txns) == {"a": 1, "b": 2, "c": 3, "d": 4}
def test_large_amounts(self):
"""Test with large transaction amounts."""
txns = [
{"amount": 1000000, "category": "salary", "date": "2024-01-01"},
{"amount": 500000, "category": "salary", "date": "2024-02-01"}
]
assert group_transactions(txns) == {"salary": 1500000}
```
---
@ -173,164 +203,161 @@ def test_many_categories():
"""
Rate Limiter
You're building an API gateway that needs to prevent abuse. Implement a
rate limiter that tracks requests per user and enforces limits using
a sliding window algorithm.
You're building an API gateway for a SaaS platform. To prevent abuse
and ensure fair usage, you need to implement a rate limiter that tracks
requests per user using a sliding window algorithm.
The rate limiter should allow at most `max_requests` per user within
any `window_seconds` time period.
The limiter should allow at most `max_requests` per user within any
`window_seconds` time period.
Example 1:
limiter = RateLimiter(max_requests=3, window_seconds=60)
limiter.allow_request("user1", timestamp=0) # True (1st request)
limiter.allow_request("user1", timestamp=30) # True (2nd request)
limiter.allow_request("user1", timestamp=45) # True (3rd request)
limiter.allow_request("user1", timestamp=50) # False (4th in 60s window)
limiter.allow_request("user1", timestamp=61) # True (1st request expired)
limiter.allow_request("user1", timestamp=50) # False (limit reached)
limiter.allow_request("user1", timestamp=61) # True (1st expired)
Example 2:
limiter = RateLimiter(max_requests=2, window_seconds=10)
limiter.allow_request("user1", timestamp=0) # True
limiter.allow_request("user2", timestamp=0) # True (different user)
limiter.allow_request("user1", timestamp=5) # True
limiter.allow_request("user1", timestamp=8) # False (limit reached)
limiter.allow_request("user1", timestamp=8) # False
Constraints:
- max_requests >= 1
- window_seconds >= 1
- timestamps are non-negative integers (seconds)
- timestamps are always non-decreasing for a given user
- Timestamps are non-negative integers (seconds)
- Timestamps are non-decreasing per user
- user_id is a non-empty string
"""
class RateLimiter:
"""Sliding window rate limiter."""
"""Sliding window rate limiter for API request throttling."""
def __init__(self, max_requests: int, window_seconds: int):
"""Initialize rate limiter with request limit and time window."""
"""Initialize with request limit and time window."""
pass # Your implementation here
def allow_request(self, user_id: str, timestamp: int) -> bool:
"""Return True if request is allowed, False if rate limited."""
"""Return True if request allowed, False if rate limited."""
pass # Your implementation here
def get_remaining(self, user_id: str, timestamp: int) -> int:
"""Return number of remaining requests allowed for user."""
"""Return remaining requests allowed for user at timestamp."""
pass # Your implementation here
```
**tests.py**:
```python
"""Tests for rate-limiter."""
import pytest
from solution import RateLimiter
def test_basic_allow():
limiter = RateLimiter(max_requests=3, window_seconds=60)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 30) == True
assert limiter.allow_request("user1", 45) == True
class TestBasicCases:
"""Test basic functionality with typical inputs."""
def test_allow_within_limit(self):
"""Test requests within the limit are allowed."""
limiter = RateLimiter(max_requests=3, window_seconds=60)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 30) == True
assert limiter.allow_request("user1", 45) == True
def test_block_over_limit(self):
"""Test requests over limit are blocked."""
limiter = RateLimiter(max_requests=2, window_seconds=60)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 30) == True
assert limiter.allow_request("user1", 45) == False
def test_multiple_users_independent(self):
"""Test each user has independent limits."""
limiter = RateLimiter(max_requests=1, window_seconds=60)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user2", 0) == True
assert limiter.allow_request("user1", 30) == False
assert limiter.allow_request("user2", 30) == False
def test_get_remaining_basic(self):
"""Test remaining count decreases with requests."""
limiter = RateLimiter(max_requests=3, window_seconds=60)
assert limiter.get_remaining("user1", 0) == 3
limiter.allow_request("user1", 0)
assert limiter.get_remaining("user1", 0) == 2
def test_rate_limit_exceeded():
limiter = RateLimiter(max_requests=2, window_seconds=60)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 30) == True
assert limiter.allow_request("user1", 45) == False
class TestEdgeCases:
"""Test edge cases and boundary conditions."""
def test_window_expiration(self):
"""Test old requests expire from window."""
limiter = RateLimiter(max_requests=2, window_seconds=60)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 30) == True
assert limiter.allow_request("user1", 45) == False
assert limiter.allow_request("user1", 61) == True
def test_window_expiration():
limiter = RateLimiter(max_requests=2, window_seconds=60)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 30) == True
assert limiter.allow_request("user1", 45) == False
assert limiter.allow_request("user1", 61) == True # First request expired
def test_single_request_limit(self):
"""Test with limit of 1 request."""
limiter = RateLimiter(max_requests=1, window_seconds=10)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 5) == False
assert limiter.allow_request("user1", 11) == True
def test_new_user_full_allowance(self):
"""Test new users start with full allowance."""
limiter = RateLimiter(max_requests=5, window_seconds=60)
limiter.allow_request("user1", 0)
assert limiter.get_remaining("new_user", 20) == 5
def test_multiple_users_independent():
limiter = RateLimiter(max_requests=1, window_seconds=60)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user2", 0) == True
assert limiter.allow_request("user1", 30) == False
assert limiter.allow_request("user2", 30) == False
def test_remaining_after_expiration(self):
"""Test remaining increases as requests expire."""
limiter = RateLimiter(max_requests=2, window_seconds=60)
limiter.allow_request("user1", 0)
limiter.allow_request("user1", 30)
assert limiter.get_remaining("user1", 30) == 0
assert limiter.get_remaining("user1", 61) == 1
def test_rapid_same_timestamp(self):
"""Test multiple requests at same timestamp."""
limiter = RateLimiter(max_requests=3, window_seconds=1)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 0) == False
def test_get_remaining():
limiter = RateLimiter(max_requests=3, window_seconds=60)
assert limiter.get_remaining("user1", 0) == 3
limiter.allow_request("user1", 0)
assert limiter.get_remaining("user1", 0) == 2
limiter.allow_request("user1", 30)
assert limiter.get_remaining("user1", 30) == 1
def test_get_remaining_after_expiration():
limiter = RateLimiter(max_requests=2, window_seconds=60)
limiter.allow_request("user1", 0)
limiter.allow_request("user1", 30)
assert limiter.get_remaining("user1", 30) == 0
assert limiter.get_remaining("user1", 61) == 1 # First expired
def test_single_request_limit():
limiter = RateLimiter(max_requests=1, window_seconds=10)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 5) == False
assert limiter.allow_request("user1", 10) == False
assert limiter.allow_request("user1", 11) == True
def test_new_user_has_full_allowance():
limiter = RateLimiter(max_requests=5, window_seconds=60)
limiter.allow_request("user1", 0)
limiter.allow_request("user1", 10)
assert limiter.get_remaining("new_user", 20) == 5
def test_rapid_requests():
limiter = RateLimiter(max_requests=3, window_seconds=1)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 0) == False
def test_exact_window_boundary(self):
"""Test behavior at exact window boundary."""
limiter = RateLimiter(max_requests=1, window_seconds=10)
assert limiter.allow_request("user1", 0) == True
assert limiter.allow_request("user1", 10) == False
assert limiter.allow_request("user1", 11) == True
```
---
## Topic Ideas by Concept
## Topic Quick Reference
### Arrays/Lists
- Remove duplicates preserving order
- Find pairs that sum to target
- Merge sorted arrays
- Rotate array by k positions
- Find missing number in sequence
- Frequency counting, deduplication, sliding window
- Two pointers, rotation, merging sorted arrays
### Strings
- Validate email/URL/phone format
- Count word frequency
- Find longest palindromic substring
- Parse CSV line with quotes
- Compress string (aaabbc -> a3b2c1)
- Validation (email, URL, phone), parsing CSV/JSON
- Pattern matching, compression, transformation
### Hash Maps
- Group items by property
- Find first non-repeating character
- Two sum / three sum variations
- LRU Cache implementation
- Anagram grouping
- Grouping by property, counting occurrences
- Two sum variants, caching, anagram detection
### Classes/OOP
- Shopping cart with discounts
- Bank account with transaction history
- Task scheduler with priorities
- Event emitter / pub-sub
- State machine implementation
- Shopping cart, bank account, task scheduler
- State machines, event systems, entity modeling
### Data Processing
- Filter and transform records
- Aggregate statistics
- Merge overlapping intervals
- Topological sort of dependencies
- Pagination with cursor
- Filter/map/reduce pipelines, aggregation
- Interval merging, pagination, deduplication