AdventOfCode.com 2016 Day 2 Solution (http://adventofcode.com/2016/day/2) (Part 1)

Day2Part1.playground.swift

import Foundation

enum Instruction:String {
    case up = "U"
    case down = "D"
    case left = "L"
    case right = "R"
}

extension Int {
    func nextDigit(withInstruction instruction:Instruction) -> Int {
    
        let keyPad = [[1,2,3],
                      [4,5,6],
                      [7,8,9]]
        var rowIdx = -1
        var colIdx = -1
        
        // Determine location of digit on keypad
        rowLoop: for row in keyPad {
            rowIdx+=1
            colIdx = -1
            for digit in row {
                colIdx+=1
                if digit == self { break rowLoop }
            }
        }
        
        // Move in the correct direction on the keypad
        switch instruction {
        case .up:
            rowIdx -= 1
        case .down:
            rowIdx += 1
        case .left:
            colIdx -= 1
        case .right:
            colIdx += 1
        }
 
        // Moved off the edge of the keypad, or self is not on the keypad
        guard rowIdx < 3, rowIdx >= 0,
            colIdx < 3, colIdx >= 0 else {
                return self
        }
        
        return keyPad[rowIdx][colIdx]
    }
}

// Day 2:
let testInput = "ULL\nRRDDD\nLURDL\nUUUUD"
let inputString = "LURLLLLLDUULRDDDRLRDDDUDDUULLRLULRURLRRDULUUURDUURLRDRRURUURUDDRDLRRLDDDDLLDURLDUUUDRDDDLULLDDLRLRRRLDLDDDDDLUUUDLUULRDUDLDRRRUDUDDRULURULDRUDLDUUUDLUDURUURRUUDRLDURRULURRURUUDDLRLDDDDRDRLDDLURLRDDLUDRLLRURRURRRURURRLLRLDRDLULLUDLUDRURDLRDUUDDUUDRLUDDLRLUDLLURDRUDDLRURDULLLUDDURULDRLUDLUDLULRRUUDDLDRLLUULDDURLURRRRUUDRUDLLDRUDLRRDUDUUURRULLDLDDRLUURLDUDDRLDRLDULDDURDLUUDRRLDRLLLRRRDLLLLURDLLLUDRUULUULLRLRDLULRLURLURRRDRLLDLDRLLRLULRDDDLUDDLLLRRLLLUURLDRULLDURDLULUDLRLDLUDURLLLURUUUDRRRULRDURLLURRLDLRLDLDRRUUDRDDDDDRDUUDULUL\nRRURLURRULLUDUULUUURURULLDLRLRRULRUDUDDLLLRRRRLRUDUUUUDULUDRULDDUDLURLRRLLDLURLRDLDUULRDLLLDLLULLURLLURURULUDLDUDLUULDDLDRLRRUURRRLLRRLRULRRLDLDLRDULDLLDRRULRDRDUDUUUDUUDDRUUUDDLRDULLULDULUUUDDUULRLDLRLUUUUURDLULDLUUUULLLLRRRLDLLDLUDDULRULLRDURDRDRRRDDDLRDDULDLURLDLUDRRLDDDLULLRULDRULRURDURRUDUUULDRLRRUDDLULDLUULULRDRDULLLDULULDUDLDRLLLRLRURUDLUDDDURDUDDDULDRLUDRDRDRLRDDDDRLDRULLURUDRLLUDRLDDDLRLRDLDDUULRUDRLUULRULRLDLRLLULLUDULRLDRURDD\nUUUUUURRDLLRUDUDURLRDDDURRRRULRLRUURLLLUULRUDLLRUUDURURUDRDLDLDRDUDUDRLUUDUUUDDURRRDRUDDUURDLRDRLDRRULULLLUDRDLLUULURULRULDRDRRLURULLDURUURDDRDLLDDDDULDULUULLRULRLDURLDDLULRLRRRLLURRLDLLULLDULRULLDLRULDDLUDDDLDDURUUUURDLLRURDURDUUDRULDUULLUUULLULLURLRDRLLRULLLLRRRRULDRULLUURLDRLRRDLDDRLRDURDRRDDDRRUDRLUULLLULRDDLDRRLRUDLRRLDULULRRDDURULLRULDUDRLRUUUULURLRLRDDDUUDDULLULLDDUDRLRDDRDRLDUURLRUULUULDUDDURDDLLLURUULLRDLRRDRDDDUDDRDLRRDDUURDUULUDDDDUUDDLULLDRDDLULLUDLDDURRULDUDRRUURRDLRLLDDRRLUUUDDUUDUDDDDDDDLULURRUULURLLUURUDUDDULURDDLRDDRRULLLDRRDLURURLRRRDDLDUUDR\nURLLRULULULULDUULDLLRDUDDRRLRLLLULUDDUDLLLRURLLLLURRLRRDLULRUDDRLRRLLRDLRRULDLULRRRRUUDDRURLRUUDLRRULDDDLRULDURLDURLRLDDULURDDDDULDRLLUDRULRDDLUUUDUDUDDRRUDUURUURLUUULRLULUURURRLRUUULDDLURULRRRRDULUDLDRLLUURRRLLURDLDLLDUDRDRLLUDLDDLRLDLRUDUULDRRLLULDRRULLULURRLDLUUDLUDDRLURDDUDRDUDDDULLDRUDLRDLRDURUULRRDRUUULRUURDURLDUDRDLLRUULUULRDDUDLRDUUUUULDDDDDRRULRURLLRLLUUDLUDDUULDRULDLDUURUDUDLRULULUULLLLRLULUDDDRRLLDRUUDRLDDDRDDURRDDDULURDLDLUDDUULUUURDULDLLULRRUURDDUDRUULDLRLURUDLRDLLLDRLDUURUDUDRLLLDDDULLUDUUULLUUUDLRRRURRRRRDUULLUURRDUU\nUDULUUDLDURRUDDUDRDDRRUULRRULULURRDDRUULDRLDUDDRRRRDLRURLLLRLRRLLLULDURRDLLDUDDULDLURLURUURLLLDUURRUUDLLLUDRUDLDDRLRRDLRLDDDULLRUURUUUDRRDLLLRRULDRURLRDLLUDRLLULRDLDDLLRRUDURULRLRLDRUDDLUUDRLDDRUDULLLURLRDLRUUDRRUUDUDRDDRDRDDLRULULURLRULDRURLURLRDRDUUDUDUULDDRLUUURULRDUDRUDRULUDDULLRDDRRUULRLDDLUUUUDUDLLLDULRRLRDDDLULRDUDRLDLURRUUDULUDRURUDDLUUUDDRLRLRLURDLDDRLRURRLLLRDRLRUUDRRRLUDLDLDDDLDULDRLURDURULURUDDDUDUULRLLDRLDDDDRULRDRLUUURD"

// Process Input
let digitStrings = inputString.components(separatedBy: "\n")
let digitInstructions = digitStrings.map { (keypath) -> [Instruction] in
    return keypath.characters.flatMap({ (instruction) -> Instruction? in
        return Instruction(rawValue: String(instruction))
    })
}

// Do the work
var currentDigit = 5

loopThroughDigits: for digit in digitInstructions {
    for instruction in digit {
        currentDigit = currentDigit.nextDigit(withInstruction: instruction)
    }
    print("\(currentDigit)")
}

Again, could be cleaned up and made more "Swifty"