C++ Cheat Sheet

• alignas
• alignof
• and
• and_eq
• asm
• atomic_cancel
• atomic_commit
• atomic_noexcept
• auto
• bitand
• bitor
• bool
• break
• case
• catch
• char
• char8_t
• char16_t
• char32_t
• class
• compl
• concept
• const
• consteval
• constexpr
• constinit
• const_cast
• continue
• co_await
• co_return
• co_yield
• decltype
• default
• delete
• do
• double
• dynamic_cast
• else
• enum
• explicit
• export
• extern
• false
• float
• for
• friend
• goto
• if
• inline
• int
• long
• mutable
• namespace
• new
• noexcept
• not
• not_eq
• nullptr
• operator
• or
• or_eq
• private
• protected
• public
• reflexpr
• register
• reinterpret_cast
• requires
• return
• short
• signed
• sizeof
• static
• static_assert
• static_cast
• struct
• switch
• synchronized
• template
• this
• thread_local
• throw
• true
• try
• typedef
• typeid
• typename
• union
• unsigned
• using
• virtual
• void
• volatile
• wchar_t
• while
• xor
• xor_eq
• final
• override
• transaction_safe
• transaction_safe_dynamic

#define LOG(msg) console.log(\_\_FILE\_\_, \_\_LINE\_\_, msg) #=> console.log("file.txt", 3, "hey") 

#define STR(name) #name char * a = STR(object); #=> char * a = "object"; 

#define DST(name) name##\_s name##\_t DST(object); #=> object_s object\_t; 

#define DEG(x) ((x) \* 57.29) 

#if VERSION == 2.0 #error Unsupported #warning Not really supported #endif 

#ifdef DEBUG console.log('hi'); #elif defined VERBOSE ... #else ... #endif 

#define FOO #define FOO "hello" #undef FOO 

#include "iostream" #include <iostream> 

• if
• elif
• else
• endif
• ifdef
• ifndef
• define
• undef
• include
• line
• error
• pragma
• defined
• __has_include
• __has_cpp_attribute
• export
• import
• module

class Vehicle { public: string brand = "Ford"; void honk() { cout << "Tuut, tuut!" << endl; } }; class Car : public Vehicle { public: string model = "Mustang"; }; Car myCar; myCar.honk(); // Output "Tuut, tuut!" cout << myCar.brand + " " + myCar.model << endl; // Output "Ford Mustang" 

class MyClass { private: int myNum; public: void setMyNum(int num) { // Setter myNum = num; } int getMyNum() { // Getter return myNum; } }; MyClass myObj; myObj.setMyNum(15); // Set the value of myNum to 15 cout << myObj.getMyNum() << endl; // Output 15 

class MyClass { public: // Public access specifier int x; // Public attribute private: // Private access specifier int y; // Private attribute protected: // Protected access specifier int z; // Protected attribute }; MyClass myObj; myObj.x = 25; // Allowed (public) myObj.y = 50; // Not allowed (private) myObj.z = 75; // Not allowed (protected) 

class MyClass { public: int myNum; string myString; void myMethod() { // Method/function defined inside the class cout << "Hello World!" << endl; } }; MyClass myObj; // Create an object of MyClass myObj.myMethod(); // Call the method 

class MyClass { public: int myNum; string myString; MyClass() { // Constructor myNum = 0; myString = ""; } ~MyClass() { // Destructor cout << "Object destroyed." << endl; } }; MyClass myObj; // Create an object of MyClass // Code here... // Object is destroyed automatically when the program exits the scope 

class MyClass { public: int myNum; string myString; MyClass() { // Constructor myNum = 0; myString = ""; } }; MyClass myObj; // Create an object of MyClass cout << myObj.myNum << endl; // Output 0 cout << myObj.myString << endl; // Output "" 

MyClass myObj; // Create an object of MyClass myObj.myNum = 15; // Set the value of myNum to 15 myObj.myString = "Hello"; // Set the value of myString to "Hello" cout << myObj.myNum << endl; // Output 15 cout << myObj.myString << endl; // Output "Hello" 

class MyClass { public: // Access specifier int myNum; // Attribute (int variable) string myString; // Attribute (string variable) }; 

#include <iostream> #include <cmath> // import library int main() { // sqrt() is from cmath std::cout << sqrt(9); } 

void fun(string a, string b) { std::cout << a + " " + b; } void fun(string a) { std::cout << a; } void fun(int a) { std::cout << a; } 

#include <iostream> int add(int a, int b) { return a + b; } int main() { std::cout << add(10, 20); } 

add is a function taking 2 ints and returning int

for (int i = 0, j = 2; i < 3; i++, j--){ std::cout << "i=" << i << ","; std::cout << "j=" << j << ";"; } // Outputs: i=0,j=2;i=1,j=1;i=2,j=0; 

int password, times = 0; while (password != 1234) { if (times++ >= 3) { std::cout << "Locked!\n"; break; } std::cout << "Password: "; std::cin >> password; // input } 

for (int n : {1, 2, 3, 4, 5}) { std::cout << n << " "; } // Outputs: 1 2 3 4 5 

std::string hello = "QuickRef.ME"; for (char c: hello) { std::cout << c << " "; } // Outputs: Q u i c k R e f . M E 

#include <iostream> int main() { auto print = [](int num) { std::cout << num << std::endl; }; std::array<int, 4> arr = {1, 2, 3, 4}; std::for_each(arr.begin(), arr.end(), print); return 0; } 

while (true) { // true or 1 std::cout << "infinite loop"; } 

for (;;) { std::cout << "infinite loop"; } 

for(int i = 1; i > 0; i++) { std::cout << "infinite loop"; } 

for (int i = 0; i < 10; i++) { if (i % 2 == 0) { continue; } std::cout << i; } // Outputs: 13579 

int i = 1; do { std::cout << i++; } while (i <= 5); // Outputs: 12345 

int i = 0; while (i < 6) { std::cout << i++; } // Outputs: 012345 

int num = 2; switch (num) { case 0: std::cout << "Zero"; break; case 1: std::cout << "One"; break; case 2: std::cout << "Two"; break; case 3: std::cout << "Three"; break; default: std::cout << "What?"; break; } 

 ┌── True ──┐ Result = Condition ? Exp1 : Exp2; └───── False ─────┘ 

int x = 3, y = 5, max; max = (x > y) ? x : y; // Outputs: 5 std::cout << max << std::endl; 

int x = 3, y = 5, max; if (x > y) { max = x; } else { max = y; } // Outputs: 5 std::cout << max << std::endl; 

#Relational Operators

#Assignment Operators

#Logical Operators

#Bitwise Operators

int score = 99; if (score == 100) { std::cout << "Superb"; } else if (score >= 90) { std::cout << "Excellent"; } else if (score >= 80) { std::cout << "Very Good"; } else if (score >= 70) { std::cout << "Good"; } else if (score >= 60) std::cout << "OK"; else std::cout << "What?"; 

if (a == 10) { // do something } 

int number = 16; if (number % 2 == 0) { std::cout << "even"; } else { std::cout << "odd"; } // Outputs: even 

 j0 j1 j2 j3 j4 j5 ┌────┬────┬────┬────┬────┬────┐ i0 | 1 | 2 | 3 | 4 | 5 | 6 | ├────┼────┼────┼────┼────┼────┤ i1 | 6 | 5 | 4 | 3 | 2 | 1 | └────┴────┴────┴────┴────┴────┘ 

int x[2][6] = { {1,2,3,4,5,6}, {6,5,4,3,2,1} }; for (int i = 0; i < 2; ++i) { for (int j = 0; j < 6; ++j) { std::cout << x[i][j] << " "; } } // Outputs: 1 2 3 4 5 6 6 5 4 3 2 1 

char ref[5] = {'R', 'e', 'f'}; // Range based for loop for (const int &n : ref) { std::cout << std::string(1, n); } // Traditional for loop for (int i = 0; i < sizeof(ref); ++i) { std::cout << ref[i]; } 

┌─────┬─────┬─────┬─────┬─────┬─────┐ | 92 | 97 | 98 | 99 | 98 | 94 | └─────┴─────┴─────┴─────┴─────┴─────┘ 0 1 2 3 4 5 

std::array<int, 6> marks = {92, 97, 98, 99, 98, 94}; // Print first element std::cout << marks[0]; // Change 2th element to 99 marks[1] = 99; // Take input from the user std::cin >> marks[2]; 

std::array<int, 3> marks; // Definition marks[0] = 92; marks[1] = 97; marks[2] = 98; // Define and initialize std::array<int, 3> = {92, 97, 98}; // With empty members std::array<int, 3> marks = {92, 97}; std::cout << marks[2]; // Outputs: 0 

#include <iostream> namespace ns1 {int val(){return 5;}} int main() { std::cout << ns1::val(); } 

#include <iostream> namespace ns1 {int val(){return 5;}} using namespace ns1; using namespace std; int main() { cout << val(); } 

Namespaces allow global identifiers under a name

int i = 1; int& ri = i; // ri is a reference to i ri = 2; // i is now changed to 2 std::cout << "i=" << i; i = 3; // i is now changed to 3 std::cout << "ri=" << ri; 

ri and i refer to the same memory location.

#include <iostream> void hello(); // Declaring int main() { // main function hello(); // Calling } void hello() { // Defining std::cout << "Hello QuickRef!\n"; } 

See: Functions

for (int i = 0; i < 10; i++) { std::cout << i << "\n"; } 

See: Loops

if (a == 10) { // do something } 

See: Conditionals

// A single one line comment in C++ /\* This is a multiple line comment in C++ \*/ 

int a = 5, b = 10; std::swap(a, b); // Outputs: a=10, b=5 std::cout << "a=" << a << ", b=" << b; 

int num; std::cout << "Type a number: "; std::cin >> num; std::cout << "You entered " << num; 

int number = 5; // Integer float f = 0.95; // Floating number double PI = 3.14159; // Floating number char yes = 'Y'; // Character std::string s = "ME"; // String (text) bool isRight = true; // Boolean // Constants const float RATE = 0.8; 

int age {25}; // Since C++11 std::cout << age; // Print 25 

#include <iostream> int main() { std::cout << "Hello QuickRef\n"; return 0; } 

Compiling and running

$ g++ hello.cpp -o hello $ ./hello Hello QuickRef