Which Data Structure can be erased from beginning to its end in O(1) time??

Answer 1

An array should be the fastest to free since it is just 1 solid block of memory. Freeing a block of memory doesn't require any operations on each byte in that block. If you had a block of 1000 bytes, freeing it doesn't involve anything like setting every byte to 0, for example. A block is usually freed with just a few integers changing value.

If you don't consider an array to be a data structure, you could include array-based data structures like array-based heaps, hash tables... because completely erasing their memory would also be a matter of de-allocating the array and a few constant time operations.

A linked list would be slow to free since every node could be in a separate block of memory. This means n nodes of a linked list could take O(n) time to free.