2. set and unordered set #

Created Saturday 18 April 2020

• Works the same as hashmap, except the fact that we store only keys, no values.

**Note: **unordered_map cannot work with pair<> out of the box. Either use set or provide a hash function for the pair.

• Use set pair for coordinates and tuples, never use a hashmap.
• Sets do not give error if we try to insert duplicates, as dealing with them is their primary op.