Code Explainers
Browse the library
python
class FileManager: """A context manager that safely opens and closes a file.""" def __init__(self, path, mode="r"):
Writing context managers in Python
context-managers
resource-management
exception-handling
Intermediate
6 steps
java
public class UnionFind { private final int[] parent; private final int[] rank; private int count;
How union-find with path compression works
disjoint-set
path-compression
union-by-rank
Intermediate
7 steps
go
package calc import "testing"
Table-driven tests in Go
table-driven-tests
error-handling
subtests
Intermediate
7 steps
javascript
class Stack { #items = []; push(value) {
Building a Stack with private fields
data-structures
encapsulation
iterators
Intermediate
7 steps
typescript
import { Injectable, NestInterceptor, ExecutionContext,
How a NestJS logging interceptor works
interceptors
rxjs
logging
Intermediate
5 steps
ruby
# Curry a multi-argument lambda so it can be applied one argument at a time. add = ->(a, b, c) { a + b + c } # Proc#curry returns a curried version that collects arguments incrementally.
Currying lambdas and methods in Ruby
currying
closures
partial-application
Intermediate
7 steps
php
<?php class Entity {
PHP magic methods for dynamic attributes
magic-methods
overloading
encapsulation
Intermediate
6 steps
rust
/// A custom iterator that yields Fibonacci numbers up to a maximum value. pub struct Fibonacci { current: u64, next: u64,
Building a custom Fibonacci iterator in Rust
iterators
traits
state-machine
Intermediate
6 steps
python
from collections import deque def bfs(graph, start):
Breadth-first search and shortest paths in Python
graph-traversal
bfs
queue
Intermediate
9 steps
go
package middleware import ( "net/http"
Building a bearer-token auth middleware in Gin
middleware
authentication
closures
Intermediate
5 steps
javascript
function depthFirstSearch(graph, start) { const visited = new Set(); const order = [];
Depth-first search and pathfinding in JS
graphs
recursion
depth-first-search
Intermediate
8 steps
typescript
// A module-scoped Singleton: the single instance lives in this module's // closure and is never exposed directly. interface AppConfig {
A module-scoped Singleton in TypeScript
singleton
generics
encapsulation
Intermediate
7 steps
ruby
class ThreadSafeCounter def initialize(initial = 0) @count = initial @mutex = Mutex.new
A thread-safe counter with Mutex in Ruby
concurrency
mutex
thread-safety
Intermediate
6 steps
php
<?php namespace App\Models;
Accessors, mutators & casts in a Laravel model
eloquent
accessors
mutators
Intermediate
6 steps
python
class Typed: """A data descriptor that enforces a type and optional validation.""" def __init__(self, expected_type, validator=None):
Building a typed descriptor in Python
descriptors
validation
metaprogramming
Advanced
8 steps
java
import java.util.*; public class TopologicalSort {
Topological sort with Kahn's algorithm
graphs
topological-sort
bfs
Intermediate
6 steps
go
package handlers import ( "net/http"
Reading path parameters in Gin
routing
path-parameters
wildcards
Beginner
7 steps
javascript
// Sliding window maximum using a monotonic decreasing deque. // Returns an array of the maximum value within each window of size k. function maxSlidingWindow(nums, k) { const result = [];
Sliding window maximum with a deque
sliding-window
monotonic-deque
amortized-analysis
Advanced
7 steps