“multiset” & “multimap” - What's the point?

Question

As the question states ... I don\'t get the point about multisets / multimaps.

So, what\'s the purpose?

Answer 1

Some use cases:

multimap

• With ZIP code as a key, all people which have that ZIP code
• With account ID as key, all open orders of that person/account
• A dictionary, with per keyword various explanations

multiset

is in essence a map with a key and a integer count.

• The inventory of a shop, all products have their key and the amount still available is the value
• accumulated sales data of a shop, every time a product is sold the product id get's added to the multiset thereby increasing the amount sold