Array size ? how to dynamicalyy create it

#1

int arr[1000];
int N;
cin >>N;
for(int i=0;i<N;i++)
{
cin >> arr[i];
}

if i use this way for taking input of array , am i not wasting array size (as i fill only n input in an array of size 1000}

how to avoid this

#2

use dynamic allocation of array

int *arr=new int [n];
using this an array of size n only is created