2nd December solution - Advent of Code 2020

december02_1.swift

let validPasswordsCount = passwords
    .map { password -> DataEntry in
        let substrings = password.split(separator: " ")
        let minMaxSub = substrings[0].split(separator: "-")
        return DataEntry(min: Int(minMaxSub[0])!, max: Int(minMaxSub[1])!, char: substrings[1].first!, password: String(substrings[2]))
    }
    .filter(isValid_1)
    .count
print(validPasswordsCount)

func isValid_1(entry: DataEntry) -> Bool {
    let occurrences = entry.password.countOccurrencesOf(char: entry.char)
    return occurrences >= entry.min && occurrences <= entry.max
}

december02_2.swift

let validPasswordsCount = passwords
    .map { password -> DataEntry in
        let substrings = password.split(separator: " ")
        let minMaxSub = substrings[0].split(separator: "-")
        return DataEntry(min: Int(minMaxSub[0])!, max: Int(minMaxSub[1])!, char: substrings[1].first!, password: String(substrings[2]))
    }
    .filter(isValid_2)
    .count
print(validPasswordsCount)

func isValid_2(entry: DataEntry) -> Bool {
    let pos1valid = entry.password.charAt(entry.min-1) == entry.char
    let pos2valid = entry.password.charAt(entry.max-1) == entry.char
    return pos1valid != pos2valid
}

december02_shared.swift

struct DataEntry {
    let min: Int
    let max: Int
    let char: Character
    let password: String
}

extension String {
    func countOccurrencesOf(char: Character) -> Int {
        return self.components(separatedBy: String(char)).count - 1
    }
    
    func charAt(_ i: Int) -> Character {
        return Array(self)[i]
    }
}

let passwords: [String] = [
"2-4 p: vpkpp",
"6-16 b: bbbbbbbbbbbbbbbpb",
"6-7 z: zzfzzdz"]