AdventOfCode.com 2016/Day 6 Solution

Day6.playground.swift

import Foundation

//: ## Helpers
func string(fromFile name:String, fileExtension:String) -> String? {
    
    if let filePath = Bundle.main.path(forResource:name, ofType:fileExtension) {
        if let inputData = FileManager.default.contents(atPath: filePath) {
            return String(data: inputData, encoding: .utf8)
        }
    }
    return nil
}


//: ## Solution Objects and Functions
enum OrderBy {
    case ascending
    case descending
}

func commonCharsString(counts:[[Character:Int]], orderedBy:OrderBy) -> String {
    let reverseSort = orderedBy == .descending
    return String(counts.flatMap {
        return $0.sorted(by: {
            if reverseSort {
                if $0.value == $1.value { return $0.key > $1.key }
                return $0.value < $1.value
            } else {
                if $0.value == $1.value { return $0.key < $1.key }
                return $0.value > $1.value
            }
        }).first?.key
    })
}

//: ## Input Processing
let day = "Day6"

let testInput = "eedadn\ndrvtee\neandsr\nraavrd\natevrs\ntsrnev\nsdttsa\nrasrtv\nnssdts\nntnada\nsvetve\ntesnvt\nvntsnd\nvrdear\ndvrsen\nenarar"


func prepareInput() -> [String] {
    if let inputString = string(fromFile: day, fileExtension: "txt") {
        return inputString.components(separatedBy: "\n")
    }
    return [String]()
}

let messages = prepareInput()
//let messages = testInput.components(separatedBy: "\n")


//: ## Solution Execution

//: ### Part 1
var counts = Array(repeatElement([Character:Int](), count: 8))

// Sum Characters
for message in messages {
    for (position,char) in message.characters.enumerated() {
        var count = counts[position]
        counts[position][char] = counts[position][char]?.advanced(by: 1) ?? 1
    }
}

let mostCommonMessage = commonCharsString(counts: counts, orderedBy: .descending)
print("Part 1 Answer: \(mostCommonMessage)\n")

//: ### Part 2
let leastCommonMessage = commonCharsString(counts: counts, orderedBy: .ascending)
print("Part 2 Answer: \(leastCommonMessage)")