Pointer pointer array with expansion.

10DynamicPointerPointerDetailed.cpp

// Example 40
// https://www.youtube.com/watch?v=c2qx13d4YG4&list=PL6xSOsbVA1eaxY06L5ZZJfDZSohwO6AKY&index=41
// C++ Example 40 - Dynamic Pointer-pointer array detailed walkthrough

#include <iostream>
#include <string>

using namespace std;

void expand(int**& arr, int& cap, int nrOfEl)
{
	// Step 1 increase capacity:
	cap *= 2;

	// Step 2 create temp array:
	int** tempArr = new int*[cap];
	
	// Step 3 INITIALIZE TEMP ARRAY
	for (int i = 0; i < cap; ++i) {
		tempArr[i] = nullptr;
	}

	// Step 4 Copy over things from old arr
	for (int j = 0; j < nrOfEl; ++j) {
		// You can do this also
		// tempArr[j] = arr[j]
		// Or we can see from here int* ptr = new int(5)
		// Replace 5 by *arr[j]
		// new int(*arr[j])
		tempArr[j] = new int(* arr[j]);
	}

	// Step 5 Deallocate arr memory
	for (int k = 0; k < nrOfEl; ++k) {
		delete arr[k];
	}
	delete[] arr;

	// Step 6 Point arr to tempArr
	arr = tempArr;

	cout << "Array expanded. New size: " << cap << endl;
}

void add(int el, int**& arr, int& cap, int& nrOfEl)
{
	if(nrOfEl >= cap)
	{
		expand(arr, cap, nrOfEl);
	}

	arr[nrOfEl++] = new int(el);

	cout << el <<  " Element added " << "nrOfEl: " << nrOfEl << endl;
}

int main() {

	int cap = 5;
	int nrOfEl = 0;
	int** arr = new int*[cap]; // int** arr means or int** means arr is a pointer to a pointer (the first spot of arr)

	// Initialize
	for (int i = 0; i < cap ; ++i) {
		arr[i] = nullptr;
	}

	add(5, arr, cap, nrOfEl);
	add(5, arr, cap, nrOfEl);
	add(5, arr, cap, nrOfEl);
	add(5, arr, cap, nrOfEl);
	add(5, arr, cap, nrOfEl);
	add(5, arr, cap, nrOfEl);

	for (int k = 0; k < nrOfEl; ++k) {
		cout << k << " " << arr[k] << " " << *arr[k] << endl;
	}

	//Delete
	for (int j = 0; j < cap ; ++j) {
		delete arr[j];
	}

	delete[] arr;

	return 0;
}