Dynamic Arrays

Overview

Standard arrays require their size to be known at compile-time. Dynamic arrays use `new[]` to allow sizes determined at runtime based on user input.

Syntax

cpp

int size;
cin >> size;

// Allocate array on the heap
int* arr = new int[size];

// Free the array using delete[]
delete[] arr;

Common Pitfalls

In modern C++, you should almost never use raw dynamic arrays (`new[]`). Use `std::vector` instead, which handles all memory management automatically.

Interview Tips

If you use `new[]` to allocate, you MUST use `delete[]` to free. Using standard `delete` on an array only frees the first element and corrupts memory.

Real-World Example

Creating an array whose size is defined by the user.

example

cpp

#include <iostream>
using namespace std;

int main() {
    int numStudents;
    cout << "How many students? ";
    cin >> numStudents;
    
    // Dynamic allocation
    int* scores = new int[numStudents];
    
    for (int i = 0; i < numStudents; i++) {
        scores[i] = 100; // Everyone gets 100!
    }
    
    // Cleanup
    delete[] scores;
    return 0;
}

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