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Go

667 problems50 sections📅 2026 curriculum

Learn Go by typing simple, idiomatic code.

Practice Go's deliberate simplicity by typing it: goroutines and channels, interfaces, structs, and the explicit if err != nil error handling that defines the language. Each snippet is idiomatic Go, and an AI tutor explains every line — how a channel synchronizes goroutines, why interfaces are satisfied implicitly — so concurrency clicks as your fingers learn the syntax.

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Run Go on your machine

1. Install the toolchain

brew install go # or: sudo apt install golang

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

go run hello.go

Official install docs ↗

progress by section

1Fundamentals0/10start →

Hello, Go Functions Basic types var and :=for is the only loop if with an init statement Printf verbs switch without fallthrough const and iota Multiple return values

2Strings In Depth0/17start →

Concatenation and length Case and trimming Contains, HasPrefix, HasSuffix Count and Repeat Sprintf builds a string Strings are immutable; []byte is not Fields splits on whitespace Indexing gives a byte Index finds an offset Replace and ReplaceAll Slice by byte range Split and Join strconv converts numbers strings.Builder range decodes UTF-8 Runes are code points unicode/utf8

3Values & References0/15start →

Go passes by value & and *Maps are reference-like new allocates a zero value The nil pointer Pointers mutate the caller Slices are reference-like Struct assignment copies Pointer to a struct Swap via pointers Arrays copy on pass Pointer receiver mutates range gives copies Return a local's address Value receiver gets a copy

4Slices & Arrays0/16Unlock →

Slice literal append Slice a range slices.Contains and Index copy builtin slices.Equal make with len and cap The nil slice slices.Reverse sort.Ints and sort.Strings 2D slices Sub-slices alias memory Delete an index sort.Slice Insert at an index Three-index slice

5Data structures0/10Unlock →

Slice basics Fixed-size arrays Maps with comma-ok Structs and literals Counting with a map Nested structs Slice as a queue Slice as a stack Structs with methods Map of slices

6Iterators0/15Unlock →

Filter with a loop Transform with a loop range over an integer range over a slice Drop the index with _range over a string A closure generator range over a map bufio.Scanner by line bufio.Scanner by word slices.Collect range over a channel iter.Seq range-over-func iter.Seq2 key/value break stops an iterator

7Traits0/21Unlock →

8Generics0/15Unlock →

comparable constraint A generic function Type inference cmp.Ordered constraint Generic stdlib helpers A generic struct Two type parameters A generic Filter Generic map keys A generic Map Generic min over a slice A generic stack A type-union constraint A generic Reduce ~ approximates underlying types

9Lifetimes0/20Unlock →

10Closures0/16Unlock →

A function literal defer Functions are values Callbacks Capturing variables Function as an argument A running total A stateful closure Currying defer evaluates args now defer with a closure Per-iteration variables A map of closures Returning a closure A slice of closures Higher-order compose

11Pattern Matching0/15Unlock →

Multiple assignment switch on values Several values per case The err != nil idiom comma-ok on a map Destructure returns switch with an init switch on strings switch true fallthrough Type assertion, comma-ok comma-ok on a channel Type switch Grouped type cases Dispatch on shapes

12Error Handling0/20Unlock →

13Option & Result0/20Unlock →

14Conversions0/15Unlock →

strconv.Atoi byte and rune []byte and string strconv.Itoa Numeric conversion T(x)strconv ParseBool/FormatBool strconv.ParseFloat fmt.Sprint and Sprintf Float to int truncates strconv.FormatInt %x and %b formatting strconv.Quote []rune and string Indexing a string strconv.ParseInt with a base

15Collection Conversions0/19Unlock →

Flatten nested slices Map keys to a slice Map values to a slice Pairs to a map Set membership Set to sorted slice slices.Contains and Index Slice to a set Sort then compact Frequency map Map to sorted pairs maps.Clone Slice to index map Iterate in key order Two slices to a map Dedup keeping order Group by a key Invert a map Set intersection

16Math0/14Unlock →

Math constants Float functions Integer arithmetic min, max, clamp Rounding Logarithms & exp Trigonometry Bit math Greatest common divisor hypot & atan2 Primality test Modulo and sign Big factorial Mean, median, stdev

17Encoding0/22Unlock →

18Random0/20Unlock →

19Data I/O0/19Unlock →

Parse CSV into rows Tab-separated values Build a CSV string Select one column CSV into a number matrix Split off the header Serialize a struct to JSON Whitespace-separated matrix Read a data file Serialize records to CSV Skip blanks and comments Print an aligned table Write CSV to a file Write a matrix as text Append a row Stream lines with a Scanner Parse JSON into a struct Parse key=value config Drop unparseable rows

20Linear Algebra0/21Unlock →

21Text Processing0/16Unlock →

Count occurrences Word count Replace text Reverse word order Count vowels Zero-pad a number Pad and align Byte offset of each rune Capitalize the first letter Character frequency Longest word Number the lines Strip all whitespace Title case Truncate with an ellipsis Levenshtein distance

22Date & Time0/12Unlock →

Add and subtract times Duration arithmetic Duration units Format a time Seconds to HH:MM:SS Parse a time Elapsed time Time a block of work UNIX timestamp round-trip Weekday and leap year Break a Duration into parts Parse a clock string

23Memory0/12Unlock →

Swap without a temp Zero values copy a slice make builds slices, maps, channels new allocates a zeroed value Pointers Trigger and read the GC Maps are reference types unsafe.Sizeof Slices alias their array append may reallocate sync.Pool

24Modules0/20Unlock →

25Macros0/20Unlock →

26Testing0/20Unlock →

27Algorithms0/10Unlock →

Greatest common divisor Binary search Linear congruential generator sort.Search Two-pointer palindrome Memoized Fibonacci Merge sorted slices Fisher-Yates shuffle Two sum Quicksort

28Sorting Algorithms0/12Unlock →

sort.Ints Bubble sort Descending order Insertion sort Selection sort sort.Slice Counting sort sort.SliceStable Merge sort Heapsort by hand container/heap Quicksort in place

29Expression Parsing0/6Unlock →

Evaluate postfix (RPN)Tokenize an expression Evaluate infix Recursive-descent calculator Right-associative power Shunting-yard

30Idioms0/9Unlock →

The comma-ok idiom defer runs LIFO Act, then check err iota enums Small interfaces The Stringer interface Table-driven cases Struct embedding Functional options

31OOP & Traits0/8Unlock →

Structs and methods Constructor function Encapsulation by case Pointer receiver Value receiver Overriding a promoted method Struct embedding Polymorphism via interfaces

32Trait Objects0/14Unlock →

Interface parameter A heterogeneous []any A pipeline of funcs Return an interface Slice of interface values Type switch Recover the concrete type Interface embedding another Embed an interface in a struct A function registry A shared interface value Command dispatch map Typed nil vs nil interface Probe for an optional interface

33Design Patterns0/14Unlock →

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

34Async0/3Unlock →

Go has no async/await Cancellation with context A channel pipeline

35File I/O0/6Unlock →

Read a file Write a file Round-trip a temp file Append with OpenFile Read lines with a Scanner Copy a file with io.Copy

36Filesystem0/18Unlock →

Does a path exist?Copy a file Create nested directories Files vs directories Build a path List a directory Rename or move Change the extension File metadata Path components Remove files and trees Sorted listing Write to a temp dir Absolute path Filter by extension Last modified time Total size of a tree Walk the tree

37Networking0/16Unlock →

Classify an IP address Split host and port Parse a URL Read a line from a stream A read deadline Bind an ephemeral port An HTTP client Resolve a hostname Parse an HTTP request Routing with ServeMux Dial a TCP server ReadFromUDP gives the sender UDP send and receive A goroutine per connection TCP echo over an ephemeral port A tiny HTTP server

38Concurrency0/7Unlock →

Start a goroutine Capture data in a goroutine Message passing with a channel Shared state with a Mutex A worker pool Atomic counters RWMutex

39Unsafe & FFI0/14Unlock →

A function value Read through unsafe.Pointer unsafe.Sizeof unsafe.Add unsafe.Alignof Calling C with cgo Write through a pointer unsafe.Offsetof Struct memory layout Pointer arithmetic with uintptr Reinterpret bits as a float unsafe.Slice String and byte reinterpret Simulating a union

40Commands0/14Unlock →

Command-line arguments Skip the program name Env var with a default Read an environment variable Current directory Iterate all env vars Set and unset a variable Exit with a code Pass env to a child Parse flags Run a command Start and wait Command exit status Read all of stdin

41Array0/10Unlock →

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

42Binary0/5Unlock →

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

43String0/10Unlock →

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

44Matrix0/4Unlock →

Rotate Image Set Matrix Zeroes Spiral Matrix Word Search

45Interval0/5Unlock →

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

46Linked List0/6Unlock →

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

47Tree0/14Unlock →

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

48Graph0/8Unlock →

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

49Heap0/3Unlock →

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

50Dynamic 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