declare dynamic array c 2b 2b

1int main()
2{
3  int size;
4
5  std::cin >> size;
6
7  int *array = new int[size];
8
9  delete [] array;
10
11  return 0;
12}

1int* a = NULL;   // Pointer to int, initialize to nothing.
2int n;           // Size needed for array
3cin >> n;        // Read in the size
4a = new int[n];  // Allocate n ints and save ptr in a.
5for (int i=0; i<n; i++) {
6    a[i] = 0;    // Initialize all elements to zero.
7}
8. . .  // Use a as a normal array
9delete [] a;  // When done, free memory pointed to by a.
10a = NULL;     // Clear a to prevent using invalid memory reference.
11

1#include <iostream>
2#include <cstddef> // std::size_t
3 
4int main()
5{
6    std::cout << "Enter a positive integer: ";
7    std::size_t length{};
8    std::cin >> length;
9 
10    int *array{ new int[length]{} }; // use array new.  Note that length does not need to be constant!
11 
12    std::cout << "I just allocated an array of integers of length " << length << '\n';
13 
14    array[0] = 5; // set element 0 to value 5
15 
16    delete[] array; // use array delete to deallocate array
17 
18    // we don't need to set array to nullptr/0 here because it's going to go out of scope immediately after this anyway
19 
20    return 0;
21}

1int length = 50;
2int *array = new int[length]();
3// returns 50 length array of 0