C++ Pointer Note

1. Pointer Introduction

#include <iostream>
using namespace std; 
int main(){
    int n = 5; 
    cout << &n << endl; // print the memory location of int n
    int* ptr = &n;     // create a pointer ptr points to n variable
    cout << ptr << endl;   // memory location
    cout << *ptr <<endl;   // 5
    system("pause>0");
}

2. Change array size at runtime

Since array need to declare the size, ie myArray[3] = {5, 4} , it is not allowed to change the size of the array. (Like the following example)

int main(){
    int size; 
    cout << "Input the size of the array: " << endl; 
    cin >> size; 
    int myArray[size] 
}

However, we can use “dynamic array” to change the size of the array at runtime:

int main(){
    int size; 
    cout << "Input the size of the array: "<< endl; 
    cin >> size; 
    int* myArray = new int[size]; 
    
    // print out the array
    for (int i = 0; i < size; i++){
        cout << "Array[" << i << "]: "; 
        cin >> myArray[i];
    } 
    for (int i = 0; i < size; i++){
        cout << myArray[i] << "  "; 
    }
    delete[] myArray; 
    myArray = NULL; 
    
    system("pause>0"); 
} 

Two things to be noted:

1. Use int* array_name = new int[size]; to create a dynamic array.
2. Once create the dynamic array, remember to delete using command delete[] array_name