gistfile1.txt

Build a data structure that implements the following 3 functions:

- set(key, value) → sets key and value in the data structure and returns nothing. 
- get(key) → returns the value that was set for this key (null if doesn’t exist)
- set_all(value) → sets the value for all keys that are in the data structure. Returns nothing.

The catch is that each of the functions should run in constant time - O(1).
Can assume in-memory simple single thread process.