felix-larsen

let countDiff = listOfDifferences.reduce(into: [:]) { counts, joltDiff in counts[joltDiff, default: 0] += 1 }

print(countDiff)

print((countDiff[1] ?? 0 ) * (countDiff[3] ?? 0 ))

felix-larsen

var iterations = 0
var newGrid = grid
repeat {
    grid = newGrid
    newGrid = [String]()
    for (rowIndex, row) in grid.enumerated() {
        var newRow = ""
        for (columnIndex, element) in row.enumerated() {
            if element == "L" {
                let count = countAdjacentChars(of: "#", in: grid, at: (columnIndex, rowIndex), allowedMismatches: 8)

felix-larsen

var x = 0.0
var y = 0.0
var direction = 0.0 // degrees east

lines.forEach { (line) in
    if let instruction = line.first, let amount = Double(line.dropFirst()) {
        if instruction == "E" {
            x += amount
        } else if instruction == "W" {
            x -= amount

felix-larsen

let departureTime = Int(lines[0])!
let busIds = lines[1].components(separatedBy: ",").compactMap{ Int($0) }

let minTimeToWait = busIds.map { busId in (busId, busId - (departureTime % busId)) }.min { first, second in first.1 < second.1 }!

print(minTimeToWait.0 * minTimeToWait.1)

felix-larsen

var currentMask = ""
var memory = [Int: String]()

lines.forEach { line in
    let parts = line.components(separatedBy: " = ")
    let variable = parts[0]
    let value = parts[1]
    print(variable, value)
    if variable.contains("mask") {
        currentMask = value

felix-larsen

let startingNumbers = [12,1,16,3,11,0]
var numbers = [Int : Int]()
startingNumbers.enumerated().dropLast().forEach { numbers[$0.element] = $0.offset }
var roundCount = startingNumbers.count
var currentNumber = startingNumbers.last!

//let roundEnd = 2020
let roundEnd = 30000000

while roundCount < roundEnd {

felix-larsen

struct Rule {
    let name: String
    let range1: ClosedRange<Int>
    let range2: ClosedRange<Int>
    
    func contains(value: Int) -> Bool {
        return range1.contains(value) || range2.contains(value)
    }
}

felix-larsen

import Foundation

let filename = "/Users/felix/xCodeProjects/AdventOfCode2020.playground/Resources/december17.txt"
let contents = try! String(contentsOfFile: filename)
let lines = contents.components(separatedBy: CharacterSet.newlines).filter { !$0.isEmpty }

var grid = [D4 : Bool]()
//var grid = [D3 : Bool]() // for 3D simulation

for (x,line) in lines.enumerated() {

felix-larsen

func calcNoBrackets(expression: String) -> Int {
    let parts = expression.components(separatedBy: " ")
    let numbers = parts.enumerated().filter {$0.0 % 2 == 0 && !$0.1.isEmpty }.map { $0.1.toInt() }
    let operators: [((Int,Int) -> Int)] = parts.enumerated().filter {$0.0 % 2 == 1 && !$0.1.isEmpty }.map { $0.1.trimmingCharacters(in: .whitespacesAndNewlines) }.map {
        switch $0 {
        case "*": return (*)
        case "+": return (+)
        default:
            return (+)
        }

felix-larsen

import Foundation

struct Rule {
    let condition1: [Int]?
    let condition2: [Int]?
    
    let char: Character?
}

let filename = "/Users/felix/xCodeProjects/AdventOfCode2020.playground/Resources/december19.txt"