advent-of-code/src/Utils.kt

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

fun Int.gcd(b: Int): Int = if (b == 0) this else b.gcd(this % b)
fun Long.gcd(b: Long): Long = if (b == 0L) this else b.gcd(this % b)
fun Int.lcm(b: Int): Int = this / gcd(b) * b
fun Long.lcm(b: Long): Long = this / gcd(b) * b
fun Iterable<Int>.lcm(): Int = reduce(Int::lcm)
fun Iterable<Long>.lcm(): Long = reduce(Long::lcm)

/**
 * 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
}

data class RelPos(val dc: Int, val dr: Int) {
    fun translate(c: Int, r: Int) = RelPos(c + dc, r + dr)
}

class CharGrid {

    companion object {
        val PLUS_POS = listOf(RelPos(0, -1), RelPos(-1, 0), RelPos(1, 0), RelPos(0, 1))
        val PLUS_CENTER_POS = listOf(RelPos(0, -1), RelPos(-1, 0), RelPos(0, 0), RelPos(1, 0), RelPos(0, 1))
        val CROSS_POS = listOf(RelPos(-1, -1), RelPos(1, -1), RelPos(-1, 1), RelPos(1, 1))
        val CROSS_CENTER_POS = listOf(RelPos(-1, -1), RelPos(1, -1), RelPos(0, 0), RelPos(-1, 1), RelPos(1, 1))
        val BOX_POS = listOf(
            RelPos(-1, -1), RelPos(0, -1), RelPos(1, -1),
            RelPos(-1, 0), RelPos(1, 0),
            RelPos(-1, 1), RelPos(0, 1), RelPos(1, 1)
        )
        val NINE_POS = listOf(
            RelPos(-1, -1), RelPos(0, -1), RelPos(1, -1),
            RelPos(-1, 0), RelPos(0, 0), RelPos(1, 0),
            RelPos(-1, 1), RelPos(0, 1), RelPos(1, 1)
        )
    }

    val width: Int
    val height: Int
    val data: Array<CharArray>
    val bChar: Char

    constructor(input: List<String>, borderChar: Char = ' ') {
        bChar = borderChar
        width = input[0].length
        height = input.size
        data = Array(height) { input[it].toCharArray() }
    }

    constructor(inputGrid: Array<CharArray>, borderChar: Char = ' ') {
        bChar = borderChar
        this.data = inputGrid
        width = inputGrid[0].size
        height = inputGrid.size
    }

    operator fun get(col: Int, row: Int) = getOrNull(col, row) ?: bChar
    operator fun set(col: Int, row: Int, newChar: Char?) {
        if (newChar != null && isInside(col, row)) data[row][col] = newChar
    }

    fun setOrThrow(col: Int, row: Int, newChar: Char) {
        if (!isInside(col, row)) throw IndexOutOfBoundsException("$col, $row out of bounds")
        set(col, row, newChar)
    }

    fun getOrNull(col: Int, row: Int) = if (isInside(col, row)) data[row][col] else null
    fun isInside(col: Int, row: Int) = (col in 0 until width) && (row in 0 until height)

    fun getHorizNumberValueAt(rp: RelPos) = getHorizNumberValueAt(rp.dc, rp.dr)

    fun getHorizNumberValueAt(col: Int, row: Int): Pair<Int, List<RelPos>> {
        val relPos = getHorizNumberRelPosAt(col, row)
        return relPos.map { this[col + it.dc, row + it.dr].digitToInt() }.reduce { acc, digit -> acc * 10 + digit } to relPos
    }

    fun getHorizNumberRelPosAt(col: Int, row: Int): List<RelPos> {
        val relPos = ArrayList<RelPos>(5)
        var c = 0
        while (col + c > 0 && get(col + c - 1, row).isDigit()) c--
        while (col + c < width && get(col + c, row).isDigit()) {
            relPos.add(RelPos(c, 0))
            c++
        }
        return relPos
    }

    fun copyOf() = CharGrid(Array(height) { data[it].copyOf() }, borderChar = bChar)

    fun applyWithPos(op: (grid: CharGrid, col: Int, row: Int) -> Char?) {
        for (r in 0 until height) {
            for (c in 0 until width) {
                this[c, r] = op(this, c, r)
            }
        }
    }

    fun apply(op: (content: Char) -> Char?) {
        applyWithPos { grid: CharGrid, col, row -> op(grid[col, row]) }
    }

    fun grow(
        relposes: Iterable<RelPos>, predicate: (content: Char) -> Boolean,
        op: (orgContent: Char, oldContent: Char, col: Int, row: Int) -> Char? = { orgContent: Char, _: Char, _: Int, _: Int -> orgContent }
    ): CharGrid {
        val newGrid = copyOf()
        for (r in 0 until height) {
            for (c in 0 until width) {
                if (predicate(get(c, r))) {
                    relposes
                        .map { it.translate(c, r) }
                        .filter { isInside(it.dc, it.dr) }
                        .forEach { newGrid[it.dc, it.dr] = op(this[c, r], newGrid[it.dc, it.dr], it.dc, it.dr) }
                }
            }
        }
        return newGrid
    }

    fun collect(c: Int, r: Int, relposes: Iterable<RelPos>, skipBorder: Boolean = true): List<Char> =
        if (skipBorder) {
            relposes.mapNotNull { getOrNull(c + it.dc, r + it.dr) }
        } else {
            relposes.map { get(c + it.dc, r + it.dr) }
        }

    fun addBorder(borderChar: Char = bChar): CharGrid {
        val topBottom = CharArray(width + 2) { borderChar }
        return CharGrid(Array(height + 2) {
            if (it == 0 || it == height + 1) topBottom else
                CharArray(width + 2) { r -> if (r == 0 || r == width + 1) borderChar else get(it - 1, r - 1) }
        }, borderChar)
    }

    fun debug() {
        data.joinToString("\n") { it.concatToString() }.println()
    }
}

/**
 * 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)