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C++

690 problems50 sections📅 2026 curriculum

Learn C++ by typing modern, idiomatic code.

Practice modern C++ by typing it: RAII and smart pointers, templates, move semantics, and STL containers and algorithms. Each snippet is idiomatic C++, and an AI tutor explains every line — why unique_ptr owns and shared_ptr counts, when a move avoids a copy — so the language's power becomes usable while your typing keeps pace.

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Run C++ on your machine

1. Install the toolchain

brew install gcc # or: sudo apt install build-essential

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

g++ -std=c++20 hello.cpp -o hello && ./hello

Official install docs ↗

progress by section

1Fundamentals0/15start →

Hello, C++auto and bindings Booleans Classic for loop Functions if / else if / else Numeric types std::println Conditional expression Range-based for std::string switch statement constexpr Structured bindings Filter and sum

2Strings In Depth0/15start →

std::string basics Build with push_back Concatenate Iterate characters Parse a number Compare strings contains find Format numbers substr std::string_view Take a string_view Replace all Uppercase with ranges Split with views

3Values & References0/16start →

References are aliases const& read-only borrow Pointers hold addresses std::swap Pass by value copies Dereference and address-of Mutable reference Pointers can be null Borrow big data Reference vs pointer Copy versus move std::move Return a reference unique_ptr owns the heap A reference member shared_ptr shares ownership

4Slices & Arrays0/17Unlock →

std::array contains Reverse in place Fill Safe access Sort in place Find an element Slice via iterators Rotate Sort by a key std::span subspan take and drop unique binary_search lower_bound Filter and transform

5Data structures0/13Unlock →

std::array std::vector std::map pair and tuple std::queue std::set std::stack unordered_map word count unordered_set dedup std::deque std::priority_queue A struct with methods A generic stack

6Iterators0/20Unlock →

7Traits0/20Unlock →

8Generics0/20Unlock →

9Lifetimes0/20Unlock →

10Closures0/20Unlock →

11Pattern Matching0/20Unlock →

12Error Handling0/20Unlock →

13Option & Result0/20Unlock →

14Conversions0/15Unlock →

std::to_string bool as a number char and int static_cast between numbers Parse with std::stod Parse with std::stoi String to vector<char>vector<char> to String Float to int truncates std::format numeric_limits std::from_chars Guard against narrowing std::to_chars std::bit_cast

15Collection Conversions0/19Unlock →

Extract map keys Extract map values Pairs to a map Set to sorted vector Vector to deque Vector to std::set Vector to unordered_set Flatten nested vectors Frequency count Map keys into a set Map to vector of pairs unordered_map to map Unique, keeping order Dedupe with sort + unique Group into a map Invert a map ranges::to a container Two vectors to a map ranges::to a map

16Math0/14Unlock →

min, max, clamp Math constants Float functions Integer arithmetic Rounding Factorial GCD and LCM Logarithms & exp Trigonometry hypot & atan2 Primality test Midpoint fmod & epsilon compare Mean, median, stddev

17Encoding0/22Unlock →

18Random0/20Unlock →

19Data I/O0/18Unlock →

Parse CSV into rows Tab-separated values Build a CSV string Select one column CSV into a number matrix Split off the header 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 from a file Parse key=value config Round-trip write then read Drop unparseable rows

20Linear Algebra0/21Unlock →

21Text Processing0/16Unlock →

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

22Date & Time0/12Unlock →

Duration literals Duration units Seconds to HH:MM:SS Current time, formatted Calendar dates Break a duration into parts Days between dates Parse a clock string Time point arithmetic Day of the week Parse a date Time zones

23Memory0/12Unlock →

Manual new and delete Swap two values Replace and return the old sizeof and alignof Move out of a value shared_ptr ownership unique_ptr ownership Reference counting Move vs copy Placement new Vector capacity growth Weak references

24Modules0/20Unlock →

25Macros0/20Unlock →

26Testing0/20Unlock →

27Algorithms0/8Unlock →

Greatest common divisor Shuffle a deck Binary search Linear congruential generator Merge two sorted ranges Palindrome check Fibonacci with memoization Two sum

28Sorting Algorithms0/12Unlock →

Check if sorted Standard library sorts Bubble sort Insertion sort ranges::sort with a projection Selection sort Counting sort Merge sort Shell sort Heapsort Quicksort Radix sort

29Expression Parsing0/6Unlock →

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

30Idioms0/9Unlock →

Range-based for Ranges pipeline emplace_back std::format output if with an initializer optional over sentinels Structured bindings RAII ownership std::span parameters

31OOP & Traits0/8Unlock →

Encapsulation Abstract base class Composition over inheritance Non-virtual template method Dynamic polymorphism Making a type printable Static polymorphism Interface inheritance

32Trait Objects0/14Unlock →

Shared method over a base Take a const Base&Return unique_ptr<Base>A vector of std::function Fixed type vs base pointer Shared base pointer A span of base pointers Template vs virtual Extended interface object A vector of base pointers Downcast with dynamic_cast A handler registry Closed set with variant Object holding a view

33Design Patterns0/14Unlock →

Builder Factory Method Singleton Adapter Lazy Initialization Observer Prototype Strategy Command Decorator Dependency Injection Object Pool State Actor

34Async0/3Unlock →

std::async and future.get Gather many futures packaged_task and exceptions

35File I/O0/6Unlock →

Read a whole file Write a file Append with ios::app Read lines with getline Count lines std::print to a file

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 the temp dir Absolute path Filter by extension Last modified time Walk the tree Total size of a tree

37Networking0/16Unlock →

Parse the request line Route by path Classify an IP address Build and read a socket address Bind an ephemeral port Resolve a hostname Build an HTTP response Read a line from a socket Shut down a connection TCP client with RAII Set a read timeout UDP receive UDP send TCP echo server A thread per connection Serve a web page

38Concurrency0/7Unlock →

Spawn a std::jthread Move data into a thread Producer/consumer queue Wait on a std::latch Shared counter with a mutex Lock-free counting Readers/writer with shared_mutex

39Unsafe & FFI0/14Unlock →

Dereference a raw pointer A function pointer A pointer precondition C strings and memcpy Call a C function Export a function to C A mutable global const and non-const pointers Reinterpret bits with bit_cast Raw new and delete Placement new Pointer arithmetic A span over raw bytes 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 remove a variable Path to this executable Exit with a code Pass env to a child Run a command Command exit status Read all of stdin Capture command output

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