title: Accessing the nth index of array in o(1)
body: <p>A very basic question, How we can access the nth index directly in O(1) cost? When we initialize an array, Is there some data structure built for keeping the addresses of each index (For accessing later in o(1) cost)? Otherwise it has to traverse from the beginning to the nth index in array. What is the reason for accessing the array elements it in o(1) ?</p>