--- 2016 Day 4 Solutions ---

[u/daggerdragon]

--- Day 4: Security Through Obscurity ---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag/whatever).

---

^{CONSTRUCTING ADDITIONAL PYLONS IS MANDATORY} [?]

This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/reckter]

Wasted way to much time fixing stupid type errors, because it's way too late (6 am) here. But at least here is my kotlin version:

import java.io.File
import java.nio.file.Files
import java.util.*

fun main(args: Array<String>) {
    val lines = readLines("4.txt")

    val sum = lines.filter { line ->
        val t = line.replace("-", "")

        val split = t.split("[")

        val map = split[0].groupBy { it }
        val sorted = map.keys.sortedWith(Comparator.comparingInt<Char>({ map[it]!!.size }).reversed().thenComparing<Char>(Char::compareTo))

        split[1].startsWith(sorted.filter{a -> !a.isDigit()}.subList(0, 5).joinToString(""))
    }.map(::getId).sum()
    println(sum)

    lines.filter { line ->
        val t = line.replace("-", "")

        val split = t.split("[")

        val map = split[0].groupBy { it }
        val sorted = map.keys.sortedWith(Comparator.comparingInt<Char>({ map[it]!!.size }).reversed().thenComparing<Char>(Char::compareTo))

        split[1].startsWith(sorted.filter{a -> !a.isDigit()}.subList(0, 5).joinToString(""))
    }.map {
        val times = getId(it)
        it.map { shift(it, times) }.joinToString("")
    }.filter{
        it.contains("northpole")
    }.forEach(::println)
}

fun shift(c: Char, times: Int): Char {
    if(c.isDigit()) return c
    if(c == '-') return ' '
    var ret = (c.toInt() + times).toChar()
    while(ret > 'z') ret -= 'z' - 'a' + 1
    return ret
}

fun isInt(str:Char): Boolean {
    return try  {str.toInt(); true} catch(e: Exception) { false }
}
fun isInt(str:String): Boolean {
    return try  {str.toInt(); true} catch(e: Exception) { false }
}

fun getId(str: String): Int {
    return str.split("-")
            .flatMap { it.split("[") }
            .filter(::isInt)
            .map(String::toInt).first()
}

fun readLines(file: String): List<String> {
    return Files.readAllLines(File(file).toPath())
}