Gotta Snatch 'Em All

set.from_list([2, 3, 3, 3, 1, 1, 2])
// -> set.from_list([1, 2, 3])

set.to_list(set.from_list([2, 3, 3, 3, 1, 1, 2]))
// -> [1, 2, 3]

set.new()
// -> set.from_list([])

let eighty_eight = set.from_list([88])

set.insert(eighty_eight, 88)
// -> set.from_list([88])

set.insert(eighty_eight, 89)
// -> set.from_list([88, 89])

set.delete(eighty_eight, 89)
// -> set.from_list([88])

set.contains(eighty_eight, 88)
// -> True

set.size(eighty_eight)
// -> 1

let a = set.from_list([1, 5, 10])
let b = set.from_list([1, 2, 3, 4, 5])

set.union(a, b)
// -> set.from_list([1, 2, 3, 4, 5, 10])

set.intersection(a, b)
// -> set.from_list([1, 5])

let is_small = fn(n) { x <= 3 }

set.filter(b, is_small)
// -> set.from_list([1, 2, 3])

Instructions

Your nostalgia for Blorkemon™️ cards is showing no sign of slowing down, you even started collecting them again, and you are getting your friends to join you.

In this exercise, a card collection is represented by Set(String), since duplicate cards are not important when your goal is to get all existing cards.

1. Start a collection

You really want your friends to join your Blorkemon™️ madness, and the best way is to kickstart their collection by giving them one card.

Implement new_collection, which transforms a card into a collection.

new_collection("Newthree")
// -> set.from_list(["Newthree"])

2. Grow the collection

Once you have a collection, it takes a life of its own and must grow.

Implement add_card, which takes a card and a collection, and returns a tuple with two values: a Bool that indicates if the card was already in the collection, and the collection with the card added.

add_card(set.from_list(["Newthree"]), "Scientuna")
// -> #(False, set.from_list(["Newthree", "Scientuna"]))

3. Start trading

Now that your friends are Blorkemon™️ crazy again, you can use this to grow your own collection by trading cards.

Not every trade is worth doing, or can be done at all. You cannot trade a card you don't have, and you shouldn't trade a card for one that you already have.

Implement trade_card, that takes two cards to trade (yours and theirs) and your current collection. The return value is a tuple of two values: a Bool stating if the trade is possible and worth doing, and the collection you would end up with if you did the trade (even if it's not actually possible).

trade_card("Scientuna", "Newthree", set.from_list(["Scientuna"]))
// -> #(True, set.from_list(["Newthree"]))

4. Cards they all have

You and your Blorkemon™️ enthusiast friends gather and wonder which cards are the most common.

Implement boring_cards, which takes a list of collections and returns a list of sorted cards that all collections have.

boring_cards([set.from_list(["Scientuna"]), set.from_list(["Newthree", "Scientuna"])])
// -> ["Scientuna"]

5. All of the cards

Do you and your friends collectively own all of the Blorkemon™️ cards?

Implement total_cards, which takes a list of collections and returns the total number of different cards in all of the collections.

total_cards([set.from_list(["Scientuna"]), set.from_list(["Newthree", "Scientuna"])])
// -> 2

6. Shiny for the win

Your nephew is coming to visit you soon, and you feel like impressing him. Kids like shiny things right? Blorkemon™️ cards can be shiny!

Implement shiny_cards, which takes a collection and returns a set containing all the cards that start with "Shiny ".

shiny_cards(set.from_list(["Newthree", "Scientuna", "Shiny Scientuna"]))
// -> set.from_list(["Shiny Scientuna"])