proxpero

// taken 2018-03-19 from wikipedia. https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2

enum Iso3166_1a2: String {
    case af = "AF"
    case ax = "AX"
    case al = "AL"
    case dz = "DZ"
    case `as` = "AS"
    case ad = "AD"
    case ao = "AO"

proxpero

//: Permutations
//  based on https://www.objc.io/blog/2014/12/08/functional-snippet-10-permutations/
//  but updated for Swift 2.0 (Xcode 7.0)

extension Array {
    func decompose() -> (Generator.Element, [Generator.Element])? {
        guard let x = first else { return nil }
        return (x, Array(self[1..<count]))
    }
}

proxpero

// taken 2018-03-19 from wikipedia. https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes

public enum Iso639_1: String {
    case ab = "AB"
    case aa = "AA"
    case af = "AF"
    case ak = "AK"
    case sq = "SQ"
    case am = "AM"
    case ar = "AR"

proxpero

// Swift 2.2

extension NSColor {
    
    convenience init(rgb: String) {
        
        guard rgb.characters.count == 6 else { fatalError("Invalid rgb value: \(rgb)") }
        
        let scanner = NSScanner(string: rgb)
        var hexValue: UInt32 = 0

proxpero

//: [Merging Overlapping Intervals](https://www.shiftedup.com/2015/05/17/programming-challenge-merging-overlapping-intervals)
//: Xcode 7.0, Swift 2.0

/*: Given a collection of intervals, write a function that merges all overlapping intervals and prints them out. 
For example, given [1, 3], [2, 6], [8, 10], and [7, 11], the function should print [1, 6], [7, 11]. Or given [5, 12], and [8, 10] the function should print [5, 12]. 
You can assume that the first element of each interval is always less or equal than the second element of the interval.
*/

//: Note: The challenge suggests that each interval is an `Array<Int>` where `interval.count == 2` and `interval[0] <= interval[1]`. In Swift, these intervals should be modeled by the `Range<Int>` type. I am altering the challenge to suit the language, I know. [TKO]

proxpero

public func ack(_ m: Int, _ n: Int) -> Int {
    if m == 0 { return n + 1 }
    if n == 0 { return ack(m - 1, 1) }
    return ack(m - 1, ack(m, n - 1))
}

for i in (0...5) {
    for j in (0...5) {
        print("ack(\(i), \(j)) is \(ack(i, j))")
    }

proxpero

//: Rotate a matrix 90 degrees in place
//  "Write a function to rotate an NxN matrix by 90 degrees. You should rotate it in place, meaning you can't use another matrix to perform the rotation, but instead you have to use the same given structure."
//  https://www.shiftedup.com/2015/05/10/programming-challenge-rotating-a-matrix-90-degrees-in-place

//  This implementation of a matrix is taken from Apple's own.
//  https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Subscripts.html
//  The extensions are my own.

//  Xcode 7.0, Swift 2.0

proxpero

/// Creates a sequence of tuple-3s built out of three underlying sequences.
/// Based on Zip2Seqence from the Swift Standard Library.
/// https://github.com/apple/swift/blob/9361a6b66f6f8351e89c090f604d7e1f42e2a045/stdlib/public/core/Zip.swift
///
/// - Parameters:
///   - sequence1: The first sequence or collection to zip.
///   - sequence2: The second sequence or collection to zip.
///   - sequence3: The third sequence or collection to zip.
/// - Returns: A sequence of tuple triples, where the elements of each triplet are
///   corresponding elements of `sequence1`, `sequence2`, and `sequence3`.

proxpero

// See http://proxpero.com/2017/07/11/encoding-and-decoding-custom-enums-with-associated-values-in-swift-4/
enum Barcode {
    case upc(Int, Int, Int, Int)
    case qrCode(String)
}

extension Barcode: Codable {
    init(from decoder: Decoder) throws {
        self = try Barcode.Coding.init(from: decoder).barcode()
    }

proxpero

// prepare the puzzle input
let input = loadFile(named: "day1") // convenience function in resources
    .split(separator: "\n")
    .compactMap(Int.init) // extension on Int to init? with String.Subsequence

// part 1
let part1 = input.reduce(0, +)

// part 2