Discussion on: AoC Day 3: No Matter How You Slice It

[Tiago Romero Garcia]

Javascript solution using regex capture groups (/^#(?<id>\d*)\s@\s(?<left>\d*),(?<top>\d*):\s(?<width>\d*)x(?<height>\d*)$/):

readFile.js

const fs = require('fs');
const readline = require('readline');

const readLines = (file, onLine) => {
    const reader = readline.createInterface({
        input: fs.createReadStream(file),
        crlfDelay: Infinity
    });

    reader.on('line', onLine);

    return new Promise(resolve => reader.on('close', resolve));
};

const readFile = async file => {
    const lines = [];
    await readLines(file, line => lines.push(line));  
    return lines;
}

module.exports = {
    readLines,
    readFile
};

03a.js

const { readFile } = require('./readLines');

const buildClaims = lines => {
    const claims = new Map();
    const regex = /^#(?<id>\d*)\s@\s(?<left>\d*),(?<top>\d*):\s(?<width>\d*)x(?<height>\d*)$/;
    for (let line of lines) {
        const { id, left, top, width, height } = line.match(regex).groups;
        claims.set(id, { 
            left: +left, 
            top: +top, 
            width: +width, 
            height: +height
        });
    }
    return claims;
};

const calculateOverlaps = claims => {
    const fabric = [];

    let overlaps = 0;

    for (let [id, claim] of claims.entries()) {
        const { left, top, width, height } = claim;
        const bottom = top + height;
        const right = left + width;
        for (let row = top; row < bottom; row++) {
            for (let col = left; col < right; col++) {
                if (!fabric[row]) {
                    fabric[row] = [];
                }
                if (!fabric[row][col]) {
                    fabric[row][col] = 0;
                }
                else if (fabric[row][col] === 1) {
                    overlaps++;
                }
                fabric[row][col]++;
            }
        }
    }

    return overlaps;
};

(async () => {
    const lines = await readFile('03-input.txt');

    const claims = buildClaims(lines);
    const overlaps = calculateOverlaps(claims);

    console.log(`Overlaps are ${overlaps} square inches`);
})();

03b.js

const { readFile } = require('./readLines');

const buildClaims = lines => {
    const claims = new Map();
    const regex = /^#(?<id>\d*)\s@\s(?<left>\d*),(?<top>\d*):\s(?<width>\d*)x(?<height>\d*)$/;
    for (let line of lines) {
        const { id, left, top, width, height } = line.match(regex).groups;
        claims.set(id, { 
            left: +left, 
            top: +top, 
            width: +width, 
            height: +height
        });
    }
    return claims;
};

const findNonOverlappingClaimID = claims => {
    const fabric = [];

    // Marking entries
    for (let [id, claim] of claims.entries()) {
        const { left, top, width, height } = claim;
        const bottom = top + height;
        const right = left + width;
        for (let row = top; row < bottom; row++) {
            for (let col = left; col < right; col++) {
                if (!fabric[row]) {
                    fabric[row] = [];
                }
                if (!fabric[row][col]) {
                    fabric[row][col] = 0;
                }
                fabric[row][col]++;
            }
        }
    }

    // Finding ID for the claim that doesnt overlap
    for (let [id, claim] of claims.entries()) {
        const { left, top, width, height } = claim;
        const bottom = top + height;
        const right = left + width;

        let doesClaimOverlap = false;
        for (let row = top; row < bottom; row++) {
            for (let col = left; col < right; col++) {
                if (fabric[row][col] > 1) {
                    doesClaimOverlap = true; 
                }
            }
        }

        if (!doesClaimOverlap) {
            return id;
        }
    }
};

(async () => {
    const lines = await readFile('03-input.txt');

    const claims = buildClaims(lines);
    const id = findNonOverlappingClaimID(claims);

    console.log(`The ID of the only claim that doesn't overlap is ${id}`);
})();