Advent of Code 2021

day2.js

const x = $('pre').textContent;

[...x.matchAll(/(?<dir>\w+) (?<num>\d+)/g)].reduce((p, c) => ({
    y: c.groups.dir === 'forward' ? p.y + Number(c.groups.num) : p.y,
    x: p.x + (c.groups.dir === 'up' ? Number(-c.groups.num) : c.groups.dir === 'down' ? Number(c.groups.num) : 0)
}),{x: 0, y: 0});

// ******************************************************************************************************************** Part 2
const x = $('pre').textContent;

[...x.matchAll(/(?<dir>\w+) (?<num>\d+)/g)].reduce((p, c) => {
        c.groups.num = Number(c.groups.num);
        switch(c.groups.dir) {
            case 'down': p.aim += c.groups.num; break;
            case 'up': p.aim -= c.groups.num; break;
            case 'forward': 
                p.x += c.groups.num;
                p.y += p.aim * c.groups.num;
        }
        return p;
    },
    { x: 0, y: 0, aim: 0 }
);

day3.js

const x = $('pre').textContent.trim().split('\n');

let res = [],
    gamma = '',
    epsilon = '';

x.forEach(line => {
    [...line].forEach((v, i) => {
        res[i] ??= [0, 0];
        res[i][Number(v)]++;
    });
});

for (const count of res) {
    const [a, b] = count[0] > count[1] ? [0, 1] : [1, 0];
    gamma += a;
    epsilon += b;
}

console.log({ gamma, epsilon, mult: parseInt(gamma, 2) * parseInt(epsilon, 2) });

// ******************************************************************************************************************** Part 2

const x = $('pre').textContent.trim().split('\n');

const find = (lines, i, mostCommon) => {
    let zero = 0, one = 0;
    lines.forEach(line => line[i] === '0' ? zero++ : one++);
    return mostCommon ? (zero > one ? '0' : '1') : (one < zero ? '1' : '0');
}

let oxygen = [...x];
let scrubber = [...x];

for (let i = 0; oxygen.length > 1; i++) {
    const max = find(oxygen, i, true);
    oxygen = oxygen.filter(line => line[i] === max)
}

for (let i = 0; scrubber.length > 1; i++) {
    const min = find(scrubber, i, false);
    scrubber = scrubber.filter(line => line[i] === min)
}

const result = parseInt(oxygen[0], 2) * parseInt(scrubber[0], 2);

// ******************************** Part 2 V2

const x = $('pre').textContent.trim().split('\n');
const types = ['scrubber', 'oxygen'].map(e => ({ name: e, lines: [...x] }));

const find = ({ lines }, i, mostCommon) => {
    let zero = [], one = [];
    lines.forEach(line => (line[i] === '0' ? zero : one).push(line));
    return mostCommon 
        ? (zero.length > one.length ? zero : one) 
        : (one.length < zero.length ? one : zero);
}

types.forEach(type => {
    for (let i = 0; type.lines.length > 1; i++) 
        type.lines = find(type, i, type.name === 'oxygen');
})

const result = types.reduce((p, c) => parseInt(p.lines[0], 2) * parseInt(c.lines[0], 2));