7th December solution - Advent of Code - swift

december07_1.swift

var list = listBagsContaining(with: bagMap, withBagName: "shinygold", allBagNames: [String]())

func listBagsContaining(with bags: [String : [Bag]], withBagName bagName: String, allBagNames: [String]) -> [String] {
    let containingBagNames = bags.filter {
        key, value in
        value.map({ $0.name}).contains(bagName)
    }
    .compactMap { $0.key }
    if containingBagNames.count == 0 {
        return allBagNames + [bagName]
    } else {
        return allBagNames + containingBagNames.flatMap({ bag in
            return listBagsContaining(with: bags, withBagName: bag, allBagNames: allBagNames + [bagName])
        })
    }
}
// subtract one as shiny gold bag is not counted
print(Set(list).count - 1)

december07_2.swift

var shinyGoldCount = countBagsContained(with: bagMap, in: Bag(name: "shinygold", count: 1), startCount: 0)

func countBagsContained(with bags : [String : [Bag]], in bag: Bag, startCount: Int) -> Int {
    let containingBagNames = bags[bag.name]
    
    if containingBagNames?.count == 0 || containingBagNames == nil {
        return startCount
    } else {
        return startCount + bag.count * containingBagNames!.reduce(0,{ start, aBag in
            return start + countBagsContained(with: bags, in: aBag, startCount: aBag.count)
        })
    }
}
print(shinyGoldCount)

december07_shared.swift

let filename = "/Users/felix/xCodeProjects/AdventOfCode2020.playground/Resources/december07.txt"
let contents = try! String(contentsOfFile: filename)
let lines = contents.components(separatedBy: CharacterSet.newlines)

struct Bag : Hashable {
    let name: String
    let count: Int
}

var bagMap = [String : [Bag]]()
lines.forEach { (line) in
    if !line.isEmpty {
    
        let splittedFirstPart = line.components(separatedBy: " contain ")
        let bagName = splittedFirstPart[0].components(separatedBy: " ")
        let bag = bagName[0] + bagName[1]
        var containingBags = [Bag]()
        let containingBagsString = splittedFirstPart[1].components(separatedBy: ", ")
        containingBagsString.forEach { (containingBagString) in
            let bagParts = containingBagString.components(separatedBy: " ")
            if !bagParts.contains("no") {
                containingBags.append(Bag(name: bagParts[1] + bagParts[2], count: Int(bagParts[0])!))
            }
        }
        bagMap[bag] = containingBags
    }
}