How to create a dynamic array in C++?

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#include <iostream>

int main()
{
    int array_size;
    // Enter size of array
    std::cin >> array_size;


    int* arr = new int[array_size];
    for (int i = 0; i < array_size; i++) {
        arr[i] = i;
        
        std::cout << "Array index " << i << " contains " << arr[i] << std::endl;
    }

    return 0;
}

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#include <iostream>
#include <vector>

int main() {
  std::vector<int> v;
  
  // Add elements to the vector
  v.push_back(1);
  v.push_back(2);
  v.push_back(3);
  
  // Print the size of the vector
  std::cout << "Size of vector: " << v.size() << std::endl;
  
  // Access elements of the vector using the [] operator
  std::cout << "v[0] = " << v[0] << std::endl;
  std::cout << "v[1] = " << v[1] << std::endl;
  std::cout << "v[2] = " << v[2] << std::endl;
  
  return 0;
}

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Size of vector: 3
v[0] = 1
v[1] = 2
v[2] = 3