gistfile1.txt

//: Playground - noun: a place where people can play

import UIKit

struct Domino {
  let left: Int
  let right: Int

  init(string: String) {
    let split = string.componentsSeparatedByString("-")
    left = split.first.flatMap { Int($0) } ?? 0
    right = split.last.flatMap { Int($0) } ?? 0
  }

  func matches(nextDomino: Domino) -> Bool {
    return right == nextDomino.left
  }
}

func matchCount(dominoString: String) -> Int {
  let dominos = dominoString.componentsSeparatedByString(",").map { Domino(string: $0) }
  let nextDominos = Array(dominos[1..<dominos.count])

  var matches = [Int]()

  for index in 0..<nextDominos.count {
    let domino = dominos[index]
    let nextDomino = nextDominos[index]
    let lastMatch = matches.last ?? 0

    matches.append(domino.matches(nextDomino) ? lastMatch + 1 : 1)
  }
  return matches.maxElement() ?? 1
}

func readFile() -> [Int] {
  do {
    if let fileURL = NSBundle.mainBundle().URLForResource("dominos", withExtension: "txt") {
      let file = try String(contentsOfURL: fileURL)
      let lines = file.componentsSeparatedByString("\n")
      return lines.map { matchCount($0) }
    }
  } catch (let e) { print(e) }
  return []
}

readFile()