Introduction to DSA

🔹 Friend Functions and Classes

**Friend functions** and **friend classes** in **Object-Oriented Programming (OOP)** provide a way to **grant special access** to private and protected members of a class without using traditional getters and setters.

📌 Why Use Friend Functions?

Friend functions allow controlled access to **private** and **protected** members of a class.

✅ **Encapsulation with Controlled Access** – Maintains data privacy while allowing necessary access.
✅ **Better Inter-Class Collaboration** – Useful when two classes need close interaction.
✅ **Flexibility** – Allows non-member functions to access private data.

💡 Real-Life Example

Consider a **Bank Account** class where an external function calculates interest but requires access to private balance data.

🖥️ Friend Functions in C++

In C++, we use the `friend` keyword to grant function access to private members.


            #include <iostream>
            using namespace std;
            
            class BankAccount {
            private:
                double balance;
            public:
                BankAccount(double b) : balance(b) {}
                friend void showBalance(const BankAccount& acc);
            };
            
            void showBalance(const BankAccount& acc) {
                cout << "Balance: " << acc.balance << endl;
            }
            
            int main() {
                BankAccount account(1000);
                showBalance(account);
                return 0;
            }

🖥️ Friend Classes in C++

Friend classes allow another class to access private data.


            class Account {
            private:
                double balance;
            public:
                Account(double b) : balance(b) {}
                friend class Auditor;
            };
            
            class Auditor {
            public:
                void checkBalance(const Account& acc) {
                    cout << "Auditor checking balance: " << acc.balance << endl;
                }
            };
            
            int main() {
                Account acc(5000);
                Auditor auditor;
                auditor.checkBalance(acc);
                return 0;
            }

🎯 Summary