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Lua

345 problems34 sections📅 2026 curriculum

Learn Lua by typing small, idiomatic code.

Practice Lua's minimal design by typing it: tables as the one data structure, metatables for OOP and operator overloading, closures, and coroutines for cooperative multitasking. Each snippet is idiomatic Lua, and an AI tutor explains every line — how a metatable's __index drives inheritance, why closures capture upvalues — so the whole language fits in your head as your typing speeds up.

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Run Lua on your machine

1. Install the toolchain

brew install lua # or: sudo apt install lua5.4

2. Save your code as hello.lua, then compile & run

lua hello.lua

Official install docs ↗

progress by section

1Fundamentals0/14start →

Hello, world Local variables Generic for Numeric for Define a function if / elseif / else The basic types while loop Formatted strings Multiple return values nil and truthiness Integers and floats repeat / until Ternary with and/or

2Strings In Depth0/14start →

Concatenation Length with #Upper and lower case string.len and methods Long string literals Repeat a string Character codes Build from codes Find a substring string.format Substrings Iterate matches Replace with gsub Capture with match

3Values & References0/10start →

Numbers are values Aliasing a table Tables are references Strings are values == compares identity Pass a table to a function Shallow copy rawequal Rebinding a parameter is local Shallow copy shares nested tables

4Slices & Arrays0/10Unlock →

Sort in place First N elements Reverse in place Sub-array with a loop Unpack an array Last N elements Copy a range with table.move select on varargs Sort with a comparator Shift within a table

5Data structures0/12Unlock →

Tables as arrays Length of an array Join with concat Append with insert Tables as maps Insert at a position ipairs is ordered Nested tables pairs over a map A stack Mixed tables A queue

6Iterators0/12Unlock →

ipairs pairs Closure iterator: range Closure iterator: values gmatch as an iterator next()The generic-for protocol Sort records with a comparator Iterate keys in order coroutine.wrap as an iterator A filtering iterator A stateless iterator

7Closures0/13Unlock →

Capturing an upvalue An accumulator A counter Returning a function Filter a table Higher-order function Map over a table Varargs with ...Currying Reduce a table Sharing an upvalue Counting varargs Compose functions

8Pattern Matching0/12Unlock →

string.match Letter class %a Digit class %d Word class %w Anchors ^ and $Multiple captures Custom class [set]Iterate with gmatch Branch on type()Table dispatch Substitute with captures Frontier %f

9Error Handling0/12Unlock →

assert() a condition Raise with error()Protected call assert forwards args pcall success values Return nil, err xpcall with handler Cleanup with pcall Propagate with context Error objects Traceback handler Error levels

10Conversions0/10Unlock →

tonumber tostring table.concat Number and string string.byte string.char math.floor to int string.format tonumber with base Hexadecimal

11Math0/14Unlock →

Integer and float arithmetic min, max, and clamp Factorial Floor and ceiling Constants: pi and huge Random numbers Roots, absolute value, powers Float modulo with fmod Greatest common divisor Primality test Logarithms and exp Trigonometry Integers vs floats Mean, median, stdev

12Text Processing0/14Unlock →

Capitalize a word Replace with gsub Longest word Count vowels Count words Character frequency Count occurrences Padding numbers and strings Reverse word order Contains, starts, ends Split on a separator Trim whitespace Title case Levenshtein distance

13Date & Time0/10Unlock →

Current time The Unix epoch Format a timestamp Date as a table CPU time with os.clock Day of the week Difference in seconds Format a duration Build an epoch Date arithmetic

14Modules0/10Unlock →

Module constants The module table Nested namespaces Private module state Export selectively Configurable module Module factory Private helpers require a module package.loaded cache

15Algorithms0/10Unlock →

Greatest common divisor Binary search Merge sorted lists Hash-map complement Linear congruential RNG Memoized Fibonacci Fisher-Yates shuffle Two-pointer pair sum Maximum subarray Quicksort

16Sorting Algorithms0/10Unlock →

table.sort Custom comparator Bubble sort Sort records by field Insertion sort Selection sort Counting sort Merge sort Quicksort (in place)Heapsort

17Expression Parsing0/6Unlock →

Evaluate RPN Tokenize an expression Right-associative power Shunting-yard to RPN Evaluate infix Recursive-descent parser

18OOP & Traits0/12Unlock →

Method on a table Colon and self Class with new()__index for methods Shared methods, self __tostring on objects A full class Dynamic dispatch Encapsulation via closures Public table, private data Inheritance Call the parent

19Design Patterns0/14Unlock →

Factory Dependency injection Singleton Strategy Adapter Builder Command Decorator Lazy init Observer Prototype State Object pool Actor mailbox

20Metatables0/14Unlock →

__index table __add operator Default values __eq operator __index function __lt operator __tostring __call __concat operator __len __newindex rawget / rawset / rawequal __unm Read-only table

21Coroutines0/12Unlock →

Create and resume Coroutine status Wrap as a function Yield values Errors in coroutines Infinite generator isyieldable Coroutine as an iterator Producer and consumer Generator pipeline Two-way communication Cooperative scheduler

22File I/O0/8Unlock →

Read the whole file Read line by line Write a file Append mode Iterate with io.lines Round-trip a temp file Count words in a file Read numbers

23Filesystem0/8Unlock →

Does a file exist?Unique temp names Basename and dirname File extension Paths from the environment Remove a file Rename a file List a directory

24Commands0/8Unlock →

Command-line arguments Environment variables This script's name time as a command Run a shell command Exit codes Capture command output Read from stdin

25Array0/10Unlock →

Contains Duplicate Two Sum Best Time to Buy and Sell Stock Maximum Subarray Container With Most Water Find Minimum in Rotated Sorted Array Product of Array Except Self Maximum Product Subarray Search in Rotated Sorted Array 3Sum

26Binary0/5Unlock →

Missing Number Number of 1 Bits Counting Bits Reverse Bits Sum of Two Integers

27String0/10Unlock →

Valid Anagram Valid Palindrome Valid Parentheses Encode and Decode Strings Group Anagrams Longest Substring Without Repeating Characters Longest Repeating Character Replacement Longest Palindromic Substring Palindromic Substrings Minimum Window Substring

28Matrix0/4Unlock →

Rotate Image Set Matrix Zeroes Spiral Matrix Word Search

29Interval0/5Unlock →

Meeting Rooms Merge Intervals Insert Interval Non-overlapping Intervals Meeting Rooms II

30Linked List0/6Unlock →

Reverse Linked List Linked List Cycle Merge Two Sorted Lists Remove Nth Node From End Merge K Sorted Lists Reorder List

31Tree0/14Unlock →

Maximum Depth of Binary Tree Invert Binary Tree Same Tree Lowest Common Ancestor of a BST Binary Tree Level Order Traversal Subtree of Another Tree Implement Trie (Prefix Tree)Kth Smallest Element in a BST Validate Binary Search Tree Add and Search Word Construct Binary Tree from Preorder and Inorder Binary Tree Maximum Path Sum Serialize and Deserialize Binary Tree Word Search II

32Graph0/8Unlock →

Number of Connected Components Number of Islands Clone Graph Course Schedule Longest Consecutive Sequence Graph Valid Tree Alien Dictionary Pacific Atlantic Water Flow

33Heap0/3Unlock →

Kth Largest Element in an Array Top K Frequent Elements Find Median from Data Stream

34Dynamic Programming0/11Unlock →

Climbing Stairs House Robber Unique Paths Coin Change House Robber II Jump Game Combination Sum IV Decode Ways Longest Common Subsequence Longest Increasing Subsequence Word Break