Pointers & References

#include <iostream>
using namespace std;

int main() {
    int num = 42;

    // & = address-of operator
    cout << "Value:   " << num   << endl;  // 42
    cout << "Address: " << &num  << endl;  // 0x7fff...

    // int* — integer pointer
    int *ptr = &num;   // ptr holds num's address

    cout << "ptr:  " << ptr   << endl;  // address
    cout << "*ptr: " << *ptr  << endl;  // 42 — dereference

    // Pointer ने value बदलणे
    *ptr = 100;
    cout << "num is now: " << num << endl;  // 100

    // nullptr — null pointer (C++11, NULL पेक्षा safe)
    int *p = nullptr;
    if (p == nullptr) {
        cout << "Pointer is null" << endl;
    }

    return 0;
}

int num = 42;

// Reference — num चे alias
int &ref = num;  // ref आणि num same memory!

cout << num << endl;  // 42
cout << ref << endl;  // 42

ref = 100;            // ref बदलला → num पण बदलतो!
cout << num << endl;  // 100

// Pointer vs Reference
// Pointer — reassignable, nullable, * dereference लागतो
// Reference — always valid, reassign नाही, . notation

// Function parameter म्हणून reference
void increment(int &x) { x++; }

int a = 5;
increment(a);
cout << a << endl;  // 6 — original बदलला

// new — heap वर memory allocate करतो
int *p = new int(42);     // single int
cout << *p << endl;        // 42

int *arr = new int[5];    // array of 5 ints
arr[0] = 10; arr[1] = 20;

// delete — memory free करणे — MANDATORY!
delete p;
delete[] arr;  // array साठी delete[]

// Modern C++ — smart pointers (memory auto free)
#include <memory>
auto sp = make_unique<int>(42);  // unique_ptr
cout << *sp << endl;  // 42
// delete लागत नाही — scope संपल्यावर auto free!