C++ Cheat Sheet

Modern C++ syntax covering pointers, references, STL containers, templates, smart pointers, and RAII memory management.

2 PagesIntermediateApr 12, 2026

Basic Syntax

Variables, control flow, and I/O.

cpp

#include <iostream>using namespace std;int main() {    int age = 30;               // stack-allocated int    double pi = 3.14159;    string name = "Ada";        // std::string    if (age >= 18) {        cout << name << " is an adult" << endl;    }    for (int i = 0; i < 5; i++) {        cout << "Count: " << i << endl;    }    return 0;}

STL Containers

Vectors, maps, and algorithms.

cpp

#include <vector>#include <map>#include <algorithm>vector<int> nums = {5, 3, 1, 4, 2};sort(nums.begin(), nums.end());     // {1, 2, 3, 4, 5}nums.push_back(6);nums.size();                        // 6map<string, int> ages;ages["Alice"] = 30;ages.count("Alice");                // 1for (auto& [name, age] : ages) {    // structured bindings (C++17)    cout << name << ": " << age << endl;}

Smart Pointers & RAII

Automatic memory management.

cpp

#include <memory>unique_ptr<int> up = make_unique<int>(42);   // sole owner, auto-deletedshared_ptr<int> sp = make_shared<int>(10);   // reference-countedshared_ptr<int> sp2 = sp;                    // ref count = 2// avoid raw `new`/`delete` in modern C++class Widget {public:    Widget() { cout << "created" << endl; }    ~Widget() { cout << "destroyed" << endl; }  // RAII cleanup};

Core Keywords

Common modern C++ keywords.

const- declares a value or method that cannot modify state
constexpr- evaluated at compile time when possible
virtual- enables runtime polymorphism via vtable dispatch
override- marks a method as overriding a virtual base method
namespace- groups identifiers to avoid naming collisions
auto- lets the compiler deduce the variable's type
template<typename T>- defines generic functions/classes parameterized by type
nullptr- type-safe null pointer constant (replaces NULL/0)

Pro Tip

Follow the Rule of Five: if you define a destructor, copy constructor, copy assignment, move constructor, or move assignment, you likely need to define all five.

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