aoc24/solutions/02.ts

import { solvables } from "../main.ts";

import type { Solvable } from "../solvable.ts";
import { readInput } from "../utils.ts";

class DayTwo implements Solvable {
    input = readInput('02')

    public part1(): Promise<DayTwo> {
        const reports = this.input.trim().split("\n").map(line => line.split(' ').map(level => Number.parseInt(level)))
        const slidingWindow = (levels: number[]): boolean => {
            const gradients: ("ascending" | "descending")[] = []
            let [i, j] = [0, 1]
            while (j < levels.length) {
                // is unsafe if ascent / descend bigger than 3 or smaller than 1
                const diff = Math.abs(levels[i] - levels[j])
                if (diff > 3 || diff < 1) {
                    return false
                }
                // calculate positive or negative gradient
                if (levels[i] < levels[j]) {
                    gradients.push("ascending")
                } else if (levels[i] > levels[j]) {
                    gradients.push("descending")
                }
                i++
                j++
            }
            // is safe and constant gradient?
            const constantGradient = gradients.every((gradient) => gradient === "ascending") || gradients.every((gradient) => gradient === "descending")
            return constantGradient
        }
        const result = reports.map(levels => slidingWindow(levels)).filter(level_safe => level_safe === true).length
        console.log(result)

        return new Promise(() => this)
    }

    public part2(): Promise<DayTwo> {
        const reports = this.input.trim().split("\n").map(line => line.split(' ').map(level => Number.parseInt(level)))
        const slidingWindow = (levels: number[]): boolean => {
            const gradients: ("ascending" | "descending" | "stagnating")[] = []
            const diffs: number[] = []
            let [i, j] = [0, 1]
            while (j < levels.length) {
                // is unsafe if ascent / descend bigger than 3 or smaller than 1
                const diff = Math.abs(levels[i] - levels[j])
                diffs.push(diff)
                // calculate positive or negative gradient
                if (levels[i] < levels[j]) {
                    gradients.push("ascending")
                } else if (levels[i] > levels[j]) {
                    gradients.push("descending")
                } else {
                    gradients.push("stagnating")
                }
                i++
                j++
            }

            // amount of unsafe diffs
            const unsafeDiffs = diffs.filter((diff) => diff > 3 || diff < 1).length

            // how many gradients are ascending / descending?
            const ascendingAmount = gradients.filter((gradient) => gradient === "ascending").length
            const descendingAmount = gradients.filter((gradient) => gradient === "descending").length

            // accept one unsafe diff if all gradients either ascending or descending
            if (ascendingAmount === gradients.length || descendingAmount === gradients.length && unsafeDiffs === 1) return true

            // allow for one wrong gradient
            const ascendingExceptOne = ascendingAmount >= gradients.length - 1
            const descendingExceptOne = descendingAmount >= gradients.length - 1
            return ascendingExceptOne || descendingExceptOne
        }
        const result = reports.map(levels => slidingWindow(levels)).filter(level_safe => level_safe === true).length
        console.log(result)

        return new Promise(() => this)
    }
}

solvables.push(new DayTwo())