advent-of-code/src/Utils.kt

import java.io.File
import java.math.BigInteger
import java.security.MessageDigest

/**
 * Reads lines from the given input txt file.
 */
fun readInput(name: String) = File("src", "$name.txt")
    .readLines()

fun listOfIntegerLists(input: List<String>): ArrayList<List<Int>> {
    val output = ArrayList<List<Int>>()
    var currList = ArrayList<Int>()
    for (i in input) {
        if (i.isEmpty()) {
            output.add(currList)
            currList = ArrayList()
        } else {
            currList.add(i.toInt())
        }
    }
    if (currList.isNotEmpty()) {
        output.add(currList)
    }
    return output
}

fun squareLinearizedOneDigitArray(input: List<String>): IntArray {
    val dim = input.first().length
    val out = IntArray(dim * dim)
    for ((rnum, r) in input.withIndex()) {
        r.forEachIndexed { index, c -> out[rnum * dim + index] = c - '0' }
    }
    return out
}

fun twoDOneDigitArray(input: List<String>): Array<IntArray> {
    return Array(input.size) { i ->
        with(input[i]) {
            val a = IntArray(length)
            for (c in indices) {
                a[c] = get(c).digitToInt()
            }
            a
        }
    }
}

/**
 * Converts string to md5 hash.
 */
fun String.md5() = BigInteger(1, MessageDigest.getInstance("MD5").digest(toByteArray()))
    .toString(16)
    .padStart(32, '0')

/**
 * The cleaner shorthand for printing output.
 */
fun Any?.println() = println(this)