advent-of-code-2023/src/day_three.ts

import { takeWhile } from 'lodash';
import fs from "fs";
import {matchAllAndThen} from "./utils";

export class Engine {
    constructor(private readonly parts: number[][], private readonly schematic: string[][]) {
    }

    public static create(input: string, gearsOnly: boolean = false): Engine {
        const lines = input.split('\n').filter(Boolean);
        const partRegex = /\d+/g;
        const symbolRegex = gearsOnly ? /\*/g : /[^a-zA-Z\d\.]/g;

        const parts : number[][] = new Array(lines.length).fill(0).map(() => new Array(lines[0].length));
        const symbols: string[][] = new Array(lines.length).fill(0).map(() => new Array(lines[0].length));

        lines.forEach((line, lineNumber) => {
            matchAllAndThen(line, partRegex, (match, index) => {
                const parsedNumber = parseInt(match, 10);
                for (let i = index; i < index + match.length; i++) {
                    parts[lineNumber][i] = parsedNumber;
                }
            });
        });

        lines.forEach((line, lineNumber) => {
            matchAllAndThen(line, symbolRegex, (match, index) => symbols[lineNumber][index] = match);
        });

        return new Engine(parts, symbols);
    }

    public sumPartNumbers(): number {
        const partsList = this.schematic.flatMap((row, rowIndex) =>
            row.map((symbol, index) => {
                if (!symbol) return symbol;

                const partIndex = [
                    [rowIndex - 1, index - 1],
                    [rowIndex - 1, index],
                    [rowIndex - 1, index + 1],
                    [rowIndex, index - 1],
                    [rowIndex, index + 1],
                    [rowIndex + 1, index - 1],
                    [rowIndex + 1, index],
                    [rowIndex + 1, index + 1]
                ];
                return Array.from(new Set(partIndex.filter(([rowNum, col]) => rowNum >= 0 && rowNum <= this.schematic.length && index >= 0 && index <= row.length)
                    .map(([rowNum, column]) => {
                        return this.parts[rowNum][column]
                    }).filter(Boolean)))
                    .reduce((total, val) => total + val,0);
            })
        ) as number[];
        return partsList.reduce((total, partNumber) => total + partNumber, 0);
    }

    public gearRatioSums(): number {
        return  this.schematic.flatMap((row, rowIndex) =>
            row
                .map((symbol, index) => {
                const partIndex = [
                    [rowIndex - 1, index - 1],
                    [rowIndex - 1, index],
                    [rowIndex - 1, index + 1],
                    [rowIndex, index - 1],
                    [rowIndex, index + 1],
                    [rowIndex + 1, index - 1],
                    [rowIndex + 1, index],
                    [rowIndex + 1, index + 1]
                ];
                return Array.from(new Set(partIndex.filter(([rowNum, col]) => rowNum >= 0 && rowNum <= this.schematic.length && index >= 0 && index <= row.length)
                    .map(([rowNum, column]) => {
                        return this.parts[rowNum][column]
                    }).filter(Boolean)))
            })
        ).filter(list => list.length === 2)
            .reduce((total, [a, b]) => {
                return total + (a * b)
            }, 0);
    }
}

export const runDayThree = () => {
    const input = fs.readFileSync('./inputs/day_three_input.txt', 'utf8');

    console.log(Engine.create(input).sumPartNumbers())
    console.log(Engine.create(input, true).gearRatioSums())

}