Why deletion of elements of hash table using doubly-linked list is O(1)?

Question

On CLRS\'s textbook \"Introduction to Algorithm\", there\'s such paragraph on pg. 258.

We can delete an element in O(1) time if the lists are doubly linked. (Note th

Answer 1

Coding point of view: one can use unordered_map in c++ to implement this.

unordered_mapmp;

Where node* is a pointer to a structure storing the key, left and right pointers!

How to use:

If you have a value v and you want to delete that node just do:

1. Access that nodes value like mp[v].

2. Now just make its left pointer point to the node on its right.

And voila, you are done.

(Just to remind, in C++ unordered_map takes an average O(1) to access a specific value stored.)