Advent of Code 2021

Puzzle1.kt

import java.io.File

fun main(args: Array<String>) {
    day1puzzle2()
}

fun countHigher(lines:List<String>) {
    var predecessor = Int.MAX_VALUE
    var countHigher = 0

    for (line in lines) {
        val current = line?.toInt()
        if (current > predecessor) {
            countHigher++
        }

        predecessor = current
    }

    println(countHigher)
}

fun day1puzzle1() {
    val lines = File("./puzzle_input.txt").readLines()
    countHigher(lines)
}

fun day1puzzle2() {
    val lines = File("./puzzle_input.txt").readLines()
    var aggregations = ArrayList<String>()
    var aggregateSum = mutableListOf(0, 0, 0)
    var counter = 0

    for (index in lines.indices) {
        val current = lines[index]?.toInt()

        if (index % 3 == 0) {
            aggregateSum[0] = current
            aggregateSum[1] += current
            aggregateSum[2] += current

            if (counter > 0) {
                aggregations.add(aggregateSum[1].toString())
            }
        } else if (index % 3 == 1) {
            aggregateSum[0] += current
            aggregateSum[1] = current
            aggregateSum[2] += current

            if (counter > 1) {
                aggregations.add(aggregateSum[2].toString())
            }
        } else {
            aggregateSum[0] += current
            aggregateSum[1] += current
            aggregateSum[2] = current
            aggregations.add(aggregateSum[0].toString())
        }

        counter++
    }

    println("${lines.size} lines aggregated into ${aggregations.size} values")

    countHigher(aggregations)
}

Puzzle2.kt

import java.io.File

fun main() {
    day2puzzle1()
}

fun day2puzzle1() {
    println(aiming(readLines()))
}

fun aiming(lines: List<String>): Int {
    var horizontal = 0
    var depth = 0
    var aim = 0

    for (line in lines) {
        if (line.indexOf("forward") == 0) {
            val horizontalValue = line.substring(8).toInt()
            horizontal += horizontalValue
            depth += aim * horizontalValue
        } else if (line.indexOf("down") == 0) {
            aim += line.substring(5).toInt()
        } else if (line.indexOf("up") == 0) {
            aim -= line.substring(3).toInt()
        }
    }

    return horizontal * depth
}

fun processLines(lines: List<String>): Int {
    var horizontal = 0
    var depth = 0

    for (line in lines) {
        if (line.indexOf("forward") == 0) {
            horizontal += line.substring(8).toInt()
        } else if (line.indexOf("down") == 0) {
            depth += line.substring(5).toInt()
        } else if (line.indexOf("up") == 0) {
            depth -= line.substring(3).toInt()
        }
    }

    return horizontal * depth
}

fun readLines(): List<String> {
    return File("./puzzle_input_2.txt").readLines()
}