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March 03, 2025 00:34
C++
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algorithms
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C++ Cheatsheet

A comprehensive cheat sheet for C++ programming, covering syntax, data structures, standard library functions, and common algorithms.

Language Fundamentals

Basic Syntax

Include Header

 
#include <iostream>

Main Function

 
int main() {
  // Your code here
  return 0;
}

Output to Console

 
std::cout << "Hello, World!" << std::endl;

Variables Declaration

 
int age = 30;
float pi = 3.14;
std::string name = "John";

Comments

 
// Single-line comment
/*
Multi-line
comment
*/

Input from Console

 
int input_num;
std::cin >> input_num;

Data Types

int

Integer numbers

float

Floating-point numbers

double

Double-precision floating-point numbers

char

Single characters

bool

Boolean values (true or false)

std::string

Sequence of characters (from <string> header)

Operators

Arithmetic Operators: +, -, *, /, %

Assignment Operators: =, +=, -=, *=, /=, %=

Comparison Operators: ==, !=, >, <, >=, <=

Logical Operators: && (AND), || (OR), ! (NOT)

Increment/Decrement Operators: ++, --

Control Flow

Conditional Statements

If Statement

 
if (condition) {
  // Code to execute if condition is true
}

If-Else Statement

 
if (condition) {
  // Code if true
} else {
  // Code if false
}

If-Else If-Else Statement

 
if (condition1) {
  // Code if condition1 is true
} else if (condition2) {
  // Code if condition2 is true
} else {
  // Code if all conditions are false
}

Switch Statement

 
switch (expression) {
  case value1:
    // Code for value1
    break;
  case value2:
    // Code for value2
    break;
  default:
    // Default code
}

Loops

For Loop

 
for (int i = 0; i < 10; ++i) {
  // Code to repeat
}

While Loop

 
while (condition) {
  // Code to repeat
}

Do-While Loop

 
do {
  // Code to repeat
} while (condition);

Break Statement

Exits the loop.

Continue Statement

Skips the current iteration.

Range-based for loop

Used to iterate over elements in a range (e.g., arrays, vectors).

std::vector<int> nums = {1, 2, 3, 4, 5};
for (int num : nums) {
  std::cout << num << " ";
}
// Output: 1 2 3 4 5

Functions

Function Definition

Basic Structure

 
return_type function_name(parameter_list) {
  // Function body
  return value;
}

Example: Add two integers

 
int add(int a, int b) {
  return a + b;
}

Function Overloading

Defining multiple functions with the same name but different parameters.

int add(int a, int b) {
  return a + b;
}

double add(double a, double b) {
  return a + b;
}

Function Pointers

Definition

Pointers that store the address of a function.

int add(int a, int b) { return a + b; }
int (*func_ptr)(int, int) = add;
int result = func_ptr(3, 4); // result is 7

Lambda Expressions

Anonymous functions defined inline.

auto add = [](int a, int b) { return a + b; };
int result = add(5, 6); // result is 11

Standard Template Library (STL)

Containers

std::vector

Dynamic array (from <vector> header)

std::list

Doubly-linked list (from <list> header)

std::deque

Double-ended queue (from <deque> header)

std::set

Sorted set (from <set> header)

std::map

Associative array (from <map> header)

std::unordered_map

Hash table (from <unordered_map> header)

Algorithms

std::sort

Sorts a range of elements (from <algorithm> header)

std::vector<int> nums = {3, 1, 4, 1, 5, 9};
std::sort(nums.begin(), nums.end());
// nums is now {1, 1, 3, 4, 5, 9}

std::find

Finds the first occurrence of a value in a range (from <algorithm> header)

auto it = std::find(nums.begin(), nums.end(), 4);
if (it != nums.end()) {
  std::cout << "Found!" << std::endl;
}

std::transform

Applies a function to a range of elements (from <algorithm> header)

std::transform(nums.begin(), nums.end(), nums.begin(), [](int n){ return n * 2; });
// nums is now {2, 2, 6, 8, 10, 18}