Advent of Code 2020

p01a.js

document.body.textContent.trim().split('\n').map(x => Number(x))
  .flatMap((x, i, a) => a.flatMap((y, j) => i < j && x + y === 2020 ? [x * y] : []))

p01b.js

document.body.textContent.trim().split('\n').map(x => Number(x))
  .flatMap((x, i, a) =>
           a.flatMap((y, j) =>
                     a.flatMap((z, k) => i < j && j < k && x + y + z === 2020 ? [x * y * z]: [])))

p02a.js

document.body.textContent.trim().split('\n')
  .filter(x => {
    [_, l, h, c, s] = x.match(/(\d+)-(\d+) (\w): (\w+)/);
    y = s.split(c).length - 1;
    return Number(l) <= y && y <= Number(h);
  }).length

p02b.js

document.body.textContent.trim().split('\n')
  .filter(x => {
    [_, l, h, c, s] = x.match(/(\d+)-(\d+) (\w): (\w+)/);
    return s[l - 1] === c ^ s[h - 1] === c;
  }).length

p03a.js

document.body.textContent.trim().split('\n').reduce((acc, val, idx) => acc + (val[(3 * idx) % val.length] == '#'), 0)

p03b.js

[[1, 1], [3, 1], [5, 1], [7, 1], [1, 2]]
  .map(([right, down]) => document.body.textContent.trim().split('\n')
                            .reduce((acc, val, idx) => acc + (idx % down ? 0 : val[(right * idx / down) % val.length] == '#'), 0))
  .reduce((acc, val) => acc * val)

p04a.js

document.body.textContent.trim().split('\n\n')
  .map(x => new Map(x.split(/\s/).map(y => y.split(':'))))
  .map(x => 'byr iyr eyr hgt hcl ecl pid'.split(' ').every(f => x.has(f)))
  .reduce((acc, val) => acc + val)

p04b.js

fields = {
  byr: x => /^[0-9]{4}$/.test(x) && 1920 <= Number(x) && Number(x) <= 2002,
  iyr: x => /^[0-9]{4}$/.test(x) && 2010 <= Number(x) && Number(x) <= 2020,
  eyr: x => /^[0-9]{4}$/.test(x) && 2020 <= Number(x) && Number(x) <= 2030,
  hgt: x => {
    y = Number(x.slice(0, -2));
    return x.slice(-2) === 'cm' ? 150 <= y && y <= 193 : x.slice(-2) === 'in' && 59 <= y && y <= 76;
  },
  hcl: x => /^#[0-9a-f]{6}$/.test(x),
  ecl: x => 'amb blu brn gry grn hzl oth'.split(' ').includes(x),
  pid: x => /^[0-9]{9}$/.test(x),
};
document.body.textContent.trim().split('\n\n')
  .map(x => new Map(x.split(/\s/).map(y => y.split(':'))))
  .map(x => Object.entries(fields).every(([f, g]) => x.has(f) && g(x.get(f))))
  .reduce((acc, val) => acc + val)

p05a.js

document.body.textContent.trim().split('\n')
  .map(x => parseInt(x.replaceAll(/[FBLR]/g, c => { return {F: 0, B: 1, L: 0, R: 1}[c]; }), 2))
  .reduce((acc, val) => Math.max(acc, val))

p05b.js

document.body.textContent.trim().split('\n')
  .map(x => parseInt(x.replaceAll(/[FBLR]/g, c => { return {F: 0, B: 1, L: 0, R: 1}[c]; }), 2))
  .sort((a, b) => a - b)
  .filter((x, i, a) => a[i + 1] === x + 2)[0] + 1

p06a.js

document.body.textContent.trim().split('\n\n')
  .map(x => new Set(x.split('\n').join('')).size)
  .reduce((acc, val) => acc + val)

p06b.js

document.body.textContent.trim().split('\n\n')
  .map(x => x.split('\n')
             .map(y => Array.from(y))
             .reduce((acc, val) => acc.filter(y => val.includes(y))).length)
  .reduce((acc, val) => acc + val)

p07a.js

g = document.body.textContent.trim().split('\n')
    .map(x => x.replaceAll(/ bags?\.?/g, '').split(' contain '))
    .flatMap(([u, v]) => v.split(', ').map(y => [u, y.replace(/\d /g, '')]))
    .reduce((g, [u, v]) => g.has(v) ? g.get(v).push(u) && g : g.set(v, [u]), new Map());
dfs = u => (g.get(u) ?? []).reduce((acc, val) => dfs(val).forEach(x => acc.add(x)) ?? acc, new Set([u]))
dfs('shiny gold').size - 1

p07b.js

g = new Map(document.body.textContent.trim().split('\n')
    .map(x => x.replaceAll(/ bags?\.?/g, '').split(' contain '))
    .map(([u, v]) => [u, v.split(', ').filter(y => y !== 'no other')
                          .map(y => [Number(y.match(/\d/)[0]), y.replace(/\d /, '')])]));
dfs = u => 1 + g.get(u).reduce((acc, [c, v]) => acc + c * dfs(v), 0);
dfs('shiny gold') - 1

p08a.js

z = document.body.textContent.trim().split('\n').map(x => x.split(' ')).map(x => [x[0], Number(x[1])]);
nxt = (i, a, x, y) => x === 'nop' ? [i + 1, a] : x === 'acc' ? [i + 1, a + y] : [i + y, a];
f = (i, a, s) => s.has(i) ? a : s.add(i) && f(...nxt(i, a, ...z[i]), s);
f(0, 0, new Set())

p08b.js

z = document.body.textContent.trim().split('\n').map(x => x.split(' ')).map(x => [x[0], Number(x[1])]);
nxt = (i, a, x, y) => x === 'nop' ? [i + 1, a] : x === 'acc' ? [i + 1, a + y] : [i + y, a];
f = (i, a, s) => i == z.length ? [a] : s.has(i) ? [] : s.add(i) && f(...nxt(i, a, ...z[i]), s);
swap = i => z[i][0] = z[i][0].replace(/(nop|jmp)/, x => x === 'nop' ? 'jmp' : 'nop');
z.flatMap((_, i) => (swap(i), r = f(0, 0, new Set()), swap(i), r))

p09a.js

a = document.body.textContent.trim().split('\n').map(x => Number(x))
a.slice(0, -25)
  .map((_, i) => a.slice(i, i + 25))
  .map(x => x.flatMap((y, i) => x.flatMap((z, j) => i < j ? [y + z] : [])))
  .flatMap((x, i) => x.includes(a[i + 25]) ? [] : [a[i + 25]])

p09b.js

a = document.body.textContent.trim().split('\n').map(x => Number(x))
t = a.slice(0, -25)
  .map((_, i) => a.slice(i, i + 25))
  .map(x => x.flatMap((y, i) => x.flatMap((z, j) => i < j ? [y + z] : [])))
  .flatMap((x, i) => x.includes(a[i + 25]) ? [] : [a[i + 25]])[0]
a.flatMap((_, i) => a.flatMap((_, j) => i < j ? [a.slice(i, j + 1)] : []))
  .flatMap(x => x.reduce((acc, val) => acc + val) === t ? [Math.min(...x) + Math.max(...x)] : [])

p10a.js

c = document.body.textContent.trim().split('\n').map(x => Number(x))
  .sort((a, b) => a - b)
  .map((x, i, a) => a[i + 1] - x).slice(0, -1)
  .reduce((acc, val) => (acc[val] += 1, acc), [0, 0, 0, 1])
c[1] * c[3]

p10b.js

document.body.textContent.trim().split('\n').map(x => Number(x))
  .sort((a, b) => a - b)
  .reduce((acc, x, i, a) =>
          (acc[i] = x < 4,  [i - 1, i - 2, i - 3].forEach(j => acc[i] += x - a[j] < 4 ? acc[j] : 0), acc), [])
  .slice(-1)

p11a.js

a = document.body.textContent.trim().split('\n').map(x => Array.from(x));
fl = a.map(x => x.map(y => y === '.'));
h = a.map(x => x.map(y => y === '#'));
dirs = [[-1, -1], [-1, 0], [-1, 1], [0, -1], [0, 1], [1, -1], [1, 0], [1, 1]];
occ = (i, j) => dirs.reduce((acc, [x, y]) => acc + (h[i + x] && h[i + x][j + y] || 0), 0);
while (1) {
  h2 = h.reduce((acc, x, i) =>
                (acc[i] = x.reduce((acc2, y, j) =>
                                   (acc2[j] = fl[i][j] ? 0 : y ? occ(i, j) >= 4 ? 0 : 1 : occ(i, j) === 0 ? 1 : 0, acc2), []), acc), []);
  if (JSON.stringify(h) === JSON.stringify(h2)) {
    break;
  }
  h = h2;
}
JSON.stringify(h).split(1).length - 1

p11b.js

a = document.body.textContent.trim().split('\n').map(x => Array.from(x));
fl = a.map(x => x.map(y => y === '.'));
h = a.map(x => x.map(y => y === '#'));
dirs = [[-1, -1], [-1, 0], [-1, 1], [0, -1], [0, 1], [1, -1], [1, 0], [1, 1]];
occ = (i, j) => dirs.reduce((acc, [x, y]) => {
  cx = i, cy = j;
  while (1) {
    cx += x, cy += y;
    if (h[cx] == null || h[cx][cy] == null) return acc;
    if (!fl[cx][cy]) return acc + h[cx][cy];
  }
}, 0);
while (1) {
  h2 = h.reduce((acc, x, i) =>
                (acc[i] = x.reduce((acc2, y, j) =>
                                   (acc2[j] = fl[i][j] ? 0 : y ? occ(i, j) >= 5 ? 0 : 1 : occ(i, j) === 0 ? 1 : 0, acc2), []), acc), []);
  if (JSON.stringify(h) === JSON.stringify(h2)) {
    break;
  }
  h = h2;
}
JSON.stringify(h).split(1).length - 1

p12a.js

document.body.textContent.trim().split('\n')
  .map(x => x.match(/(.)(.*)/))
  .map(x => [x[1], Number(x[2])])
  .reduce(([x, y, dirx, diry], [p, q]) => {
    x += q * (({E: 1, W: -1}[p] ?? 0) + (p === 'F') * dirx);
    y += q * (({N: 1, S: -1}[p] ?? 0) + (p === 'F') * diry);
    m = {L: 1, R: -1}[p] ?? 0;
    for (i = 0; m && i < q / 90; i++) [dirx, diry] = [-m * diry, m * dirx];
    return [x, y, dirx, diry];
  }, [0, 0, 1, 0])
  .slice(0, 2)
  .reduce((acc, val) => acc + Math.abs(val), 0);

p12b.js

document.body.textContent.trim().split('\n')
  .map(x => x.match(/(.)(.*)/))
  .map(x => [x[1], Number(x[2])])
  .reduce(([x, y, dirx, diry], [p, q]) => {
    dirx += q * ({E: 1, W: -1}[p] ?? 0);
    diry += q * ({N: 1, S: -1}[p] ?? 0);
    if (p === 'F') x += q * dirx, y += q * diry;
    m = {L: 1, R: -1}[p] ?? 0;
    for (i = 0; m && i < q / 90; i++) [dirx, diry] = [-m * diry, m * dirx];
    return [x, y, dirx, diry];
  }, [0, 0, 10, 1])
  .slice(0, 2)
  .reduce((acc, val) => acc + Math.abs(val), 0);

p13a.js

[n, a] = document.body.textContent.trim().split('\n');
[n, a] = [Number(n), a.split(',').filter(x => x !== 'x').map(x => Number(x))];
a.map(x => [x * Math.ceil(n / x) - n, x])
  .reduce((acc, [y, x]) => y < acc[0] ? [y, x * y] : acc, [Infinity])

p13b.js

egcd = (a, b) => {
  if (!b) return [1n, 0n, a];
  [x, y, g] = egcd(b, a % b);
  return [y, x - y * (a / b), g];
};
document.body.textContent.trim().split('\n')[1]
  .split(',')
  .flatMap((x, i) => x === 'x' ? [] : [[BigInt(x), BigInt(-i)]])
  .reduce(([y, offy], [x, offx]) => {
    [px, py, g] = egcd(x, y);  // all primes, g = 1
    lcm = x * y;
    pos = ((offy - offx) * px * x + offx) % lcm;
    return [lcm, (pos + lcm) % lcm];
  })

p14a.js

Array.from(
   document.body.textContent.trim().split('\n')
    .reduce(([mem, ma, mo], inp) => {
      [_, m] = inp.match(/mask = ([01X]+)/) ?? [];
      if (m) {
        ma = BigInt('0b' + m.replaceAll('X', 1)), mo = BigInt('0b' + m.replaceAll('X', 0));
      } else {
        [_, pos, val] = inp.match(/mem\[(\d+)\] = (\d+)/);
        pos = BigInt(pos), val = BigInt(val);
        mem.set(pos, ma & val | mo);
      }
      return [mem, ma, mo];
    }, [new Map()])[0].values())
  .reduce((acc, val) => acc + val)

p14b.js

Array.from(
   document.body.textContent.trim().split('\n')
    .reduce(([mem, ma, mo, mx], inp) => {
      [_, m] = inp.match(/mask = ([01X]+)/) ?? [];
      if (m) {
        mo = BigInt('0b' + m.replaceAll('X', 0));
        ma = BigInt('0b' + m.replaceAll(0, 1).replaceAll('X', 0));
        mx = ((1n << 36n) - 1n) ^ ma;
      } else {
        [_, pos, val] = inp.match(/mem\[(\d+)\] = (\d+)/);
        pos = ma & BigInt(pos) | mo, val = BigInt(val);
        for (i = mx; i > 0n; i = (i - 1n) & mx) {
          mem.set(pos | i, val);
        }
        mem.set(pos, val);
      }
      return [mem, ma, mo, mx];
    }, [new Map()])[0].values())
  .reduce((acc, val) => acc + val)

p15a.js

a = document.querySelector('.puzzle-input').textContent.split(',').map(x => Number(x));
m1 = new Map(), m2 = new Map();
set = (x, i) => (m2.set(x, m1.get(x)), m1.set(x, i));
get = (x) => m1.get(x) - (m2.get(x) ?? m1.get(x));
for (i = 0; i < 2020; i++) {
  if (i < a.length) {
    set(a[i], i);
    prev = a[i];
    continue;
  }
  age = get(prev);
  set(age, i);
  prev = age;
}
prev

p15b.js

a = document.querySelector('.puzzle-input').textContent.split(',').map(x => Number(x));
m1 = new Map(), m2 = new Map();
set = (x, i) => (m2.set(x, m1.get(x)), m1.set(x, i));
get = (x) => m1.get(x) - (m2.get(x) ?? m1.get(x));
for (i = 0; i < 30000000; i++) {
  if (i < a.length) {
    set(a[i], i);
    prev = a[i];
    continue;
  }
  age = get(prev);
  set(age, i);
  prev = age;
}
prev

p16a.js

[spec, my, rest] = document.body.textContent.trim().split('\n\n');
anyOk = spec.split('\n')
  .flatMap(x => [...x.matchAll(/(\d+)-(\d+)/g)].map(([_, p, q]) => (z) => Number(p) <= z && z <= Number(q)))
  .reduce((acc, val) => (z) => acc(z) || val(z));
rest.split('\n').slice(1)
  .flatMap(x => x.split(',').map(x => Number(x)).map(x => anyOk(x) ? 0 : x))
  .reduce((acc, val) => acc + val)

p16b.js

[spec, my, rest] = document.body.textContent.trim().split('\n\n').map(x => x.split('\n'));
ok = spec.map(x => [...x.matchAll(/(\d+)-(\d+)/g)]
                .map(([_, p, q]) => (z) => Number(p) <= z && z <= Number(q))
                .reduce((acc, val) => (z) => acc(z) || val(z)));
my = my[1].split(',').map(x => Number(x));
rows = [my, ...rest.slice(1)
            .map(x => x.split(',').map(x => Number(x)))
            .filter(x => x.reduce((acc, val) => acc && ok.reduce((acc1, f) => acc1 || f(val), false), true))];
g = ok.map(f => ok.flatMap((_, i) => rows.map(r => r[i]).reduce((acc, val) => acc && f(val), true) ? [i] : []));
res = [];
g.forEach(_ => g.forEach((r, i) => {
  if (r.length === 1) j = r[0], res[i] = j, g = g.map(r => r.filter(x => x != j));
}));
spec.reduce((acc, x, i) => x.startsWith('departure') ? acc * my[res[i]] : acc, 1)

p17a.js

g = document.body.textContent.split('\n').flatMap((r, i) => [...r].flatMap((x, j) => x === '#' ? [[0, i, j]] : []));
sgfy = x => JSON.stringify(x);
nbs = ([x0, y0, z0]) => (d = [-1, 0, 1], d.flatMap(x =>
                                                  d.flatMap(y =>
                                                            d.flatMap(z => x === 0 && y === 0 && z === 0 ?
                                                                        [] : [[x + x0, y + y0, z + z0]]))));
get = p => g.find(q => sgfy(p) === sgfy(q));
keep = p => (cnt = nbs(p).filter(get).length, get(p) && cnt === 2 || cnt === 3);
for (t = 0; t < 6; t++) {
  g = [...new Set([...g.map(sgfy), ...g.flatMap(nbs).map(sgfy)])].map(x => JSON.parse(x)).filter(keep);
}
g.length

p17b.js

a = document.body.textContent.split('\n').flatMap((r, i) => [...r].flatMap((x, j) => x === '#' ? [[0, 0, i, j]] : []));
sgfy = x => JSON.stringify(x), prse = x => JSON.parse(x);
cube = dims => dims === 0 ? [[]] : (m = cube(dims - 1), [-1, 1, 0].flatMap(d => m.map(a => [d, ...a])));
cached = cube(a[0].length).slice(0, -1);
g = new Set(a.map(sgfy));
nbs = p => cached.map(q => q.map((x, i) => x + p[i]));
get = p => g.has(p);
keep = p => (cnt = nbs(p).map(sgfy).filter(get).length, get(sgfy(p)) && cnt === 2 || cnt === 3);
for (t = 0; t < 6; t++) {
  g = new Set([...new Set([...g, ...[...g].map(prse).flatMap(nbs).map(sgfy)])].map(prse).filter(keep).map(sgfy));
}
g.size

p18a.js

solve = a => {
  st = [], ost = [];
  pushop = () => st.push(eval(st.pop() + ost.pop() + st.pop()));
  for (token of a) {
    n = Number(token);
    if (!isNaN(n)) {
      st.push(n);
    } else if (token === '(') {
      ost.push(token);
    } else if (token === ')') {
      while (ost[ost.length - 1] !== '(') pushop();
      ost.pop();
    } else {
      while (ost.length && ost[ost.length - 1] !== '(') pushop();
      ost.push(token);
    }
  }
  while (ost.length) pushop();
  return st[0];
}
document.body.textContent.split('\n')
  .map(x => x.replaceAll('(', '( ').replaceAll(')', ' )').split(' '))
  .map(solve)
  .reduce((acc, val) => acc + val)

p18b.js

solve = a => {
  st = [], ost = [];
  pushop = o => st.push(eval(st.pop() + ost.pop() + st.pop()));
  for (token of a) {
    n = Number(token);
    if (!isNaN(n)) {
      st.push(n);
    } else if (token === '(') {
      ost.push(token);
    } else if (token === ')') {
      while (ost[ost.length - 1] !== '(') pushop();
      ost.pop();
    } else {
      stop = token === '+' ? '*(' : '(';
      while (ost.length && !stop.includes(ost[ost.length - 1])) pushop();
      ost.push(token);
    }
  }
  while (ost.length) pushop();
  return st[0];
}
document.body.textContent.split('\n')
  .map(x => x.replaceAll('(', '( ').replaceAll(')', ' )').split(' '))
  .map(solve)
  .reduce((acc, val) => acc + val)

p19a.js

[rules, input] = document.body.textContent.split('\n\n').map(x => x.split('\n'));
rulesMap = new Map(rules.map(x => x.split(': '))
                     .map(x => [x[0], x[1].startsWith('"') ? x[1].slice(1, -1) : x[1].split(' | ').map(y => y.split(' '))]));
makeRegex = i => {
  rule = rulesMap.get(i);
  if (typeof rule === 'string') return rule;
  return `(${rule.map(x => x.map(makeRegex).join('')).join('|')})`;
};
r = new RegExp(`^${makeRegex('0')}$`);
input.filter(x => r.test(x)).length

p19b.js

[rules, input] = document.body.textContent.split('\n\n').map(x => x.split('\n'));
rulesMap = new Map(rules.map(x => x.split(': '))
                     .map(x => [x[0], x[1].startsWith('"') ? x[1].slice(1, -1) : x[1].split(' | ').map(y => y.split(' '))]));
makeRegex = i => {
  if (i === '8') return `${makeRegex('42')}+`;
  if (i === '11') {
    a = makeRegex('42'), b = makeRegex('31');
    maxlen = input.reduce((acc, val) => Math.max(acc, val.length), 0);
    return `(${[...new Array(maxlen).keys()].map(i => `(${a}{${i + 1}}${b}{${i + 1}})`).join('|')})`;
  }
  rule = rulesMap.get(i);
  if (typeof rule === 'string') return rule;
  return `(${rule.map(x => x.map(makeRegex).join('')).join('|')})`;
};
r = new RegExp(`^${makeRegex('0')}$`);
input.filter(x => r.test(x)).length

p20a.js

borders = g => {
  r = [g[0], g[g.length - 1], g.map((_, i) => g[i][0]).join(''), g.map((_, i) => g[i][g[i].length - 1]).join('')];
  return r.concat(r.map(x => [...x].reverse().join('')));
}
document.body.textContent.trim().split('\n\n')
  .map(x => x.split('\n'))
  .map(x => ({id: Number(x[0].match(/\d+/)[0]), g: x.slice(1), borders: borders(x.slice(1))}))
  .filter((x, _, a) => x.borders.map(b => a.filter(y => y.borders.includes(b)).length).filter(c => c === 1).length === 4)
  .reduce((acc, x) => acc * x.id, 1)

p20b.js

rot90 = g => g[0].map((_, i) => g.map(r => r[i]).reverse())
lrflip = g => g.map(r => r.slice().reverse());
variations = g => {
  r0 = [g, lrflip(g)];
  r1 = r0.map(rot90);
  r2 = r1.map(rot90);
  r3 = r2.map(rot90);
  return r0.concat(r1, r2, r3);
};
topBorder = g => g[0].join('');
bottomBorder = g => g[g.length - 1].join('');
leftBorder = g => g.map(r => r[0]).join('');
rightBorder = g => g.map(r => r[r.length - 1]).join('');
trimBorders = g => g.slice(1, -1).map(r => r.slice(1, -1));

a = document.body.textContent.trim().split('\n\n')
  .map(x => x.split('\n'))
  .map(x => ({id: Number(x[0].match(/\d+/)[0]), v: variations(x.slice(1).map(r => r.split('')))}));

findMatch = (b, tf, z) => z.map(t => [t, t.v.filter(g => b === tf(g))[0]]).filter(x => x[1]);

gg = [];
populate = (g, i, j) => {
  for (ii = 0; ii < g.length; ii++) {
    gg[ii + i] = gg[ii + i] ?? [];
    gg[ii + i].splice(j, 0, ...g[ii]);
  }
}

fillCol = (top, i, j) => {
  m = findMatch(top, topBorder, [...s])[0];
  if (!m) return;
  [t, last] = m;
  s.delete(t);
  g = trimBorders(last);
  populate(g, i, j);
  fillCol(bottomBorder(last), i + g.length, j);
}

fillRow = (left, i, j) => {
  m = findMatch(left, leftBorder, [...s])[0];
  if (!m) return;
  [_, head] = m;
  fillCol(topBorder(head), i, j);
  fillRow(rightBorder(head), i, j + trimBorders(head)[0].length);
}

corners = a.filter(t => t.v.filter(g => findMatch(topBorder(g), topBorder, a.filter(u => t !== u)).length).length === 4)
s = new Set(a);
ss = [...s].filter(t => t !== corners[0]);
last = corners[0].v.filter(g => findMatch(rightBorder(g), leftBorder, ss).length && findMatch(bottomBorder(g), topBorder, ss).length)[0];
fillRow(leftBorder(last), 0, 0);

monster = `                  # 
#    ##    ##    ###
 #  #  #  #  #  #   `.split('\n').flatMap((r, i) => [...r].flatMap((c, j) => c === '#' ? [[i, j]] : []));
isMonster = (g, i, j) => monster.every(([x, y]) => g[i + x] && g[i + x][j + y] === '#');
countMonsters = g => g.flatMap((_, i) => g[0].map((_, j) => isMonster(g, i, j))).filter(x => x).length;
monsters = variations(gg).map(countMonsters).filter(x => x)[0];

String(gg).split('#').length - 1 - monsters * monster.length

p21a.js

a = document.body.textContent.trim().split('\n')
  .map(x => x.slice(0, -1).split(' (contains '))
  .map(x => ({ing: x[0].split(' '), all: x[1].split(', ')}));
bad = a.flatMap(x => x.all).flatMap(al => a.filter(x => x.all.includes(al))
                                                    .map(x => x.ing)
                                                    .reduce((acc, val) => acc.filter(i => val.includes(i))));
a.flatMap(x => x.ing).filter(i => !bad.includes(i)).length

p21b.js

a = document.body.textContent.trim().split('\n')
  .map(x => x.slice(0, -1).split(' (contains '))
  .map(x => ({ing: x[0].split(' '), all: x[1].split(', ')}));
bad = [...new Set(a.flatMap(x => x.all))].sort().map(al => a.filter(x => x.all.includes(al))
                                                       .map(x => x.ing)
                                                       .reduce((acc, val) => acc.filter(i => val.includes(i))));
ans = [];
bad.forEach(() => bad.forEach((b, i) => { if (b.length === 1) ans[i] = b[0], bad = bad.map(b => b.filter(x => x !== ans[i])); }));
ans.join(',')

p22a.js

[a, b] = document.body.textContent.trim().split('\n\n').map(x => x.split('\n').slice(1).map(x => Number(x)));
while (a.length && b.length) {
  p = a.shift(), q = b.shift();
  if (p > q) a.push(p, q);
  else b.push(q, p);
}
(a.length ? a : b).reverse().reduce((acc, val, i) => acc + val * (i + 1), 0)

p22b.js

[a, b] = document.body.textContent.trim().split('\n\n').map(x => x.split('\n').slice(1).map(x => Number(x)));
play = (a, b) => {
  let seen = new Set();
  while (a.length && b.length) {
    key = String(a) + '/' + String(b);
    if (seen.has(key)) break;
    seen.add(key);
    let p = a.shift(), q = b.shift();
    awin = a.length >= p && b.length >= q ? play(a.slice(0, p), b.slice(0, q)) : p > q;
    if (awin) a.push(p, q);
    else b.push(q, p);
  }
  return a.length;
}
(play(a, b) ? a : b).reverse().reduce((acc, val, i) => acc + val * (i + 1), 0)

p23a.js

a = [...document.querySelector('.puzzle-input').textContent].map(x => Number(x));
for (i = 0; i < 100; i++) {
  x = a.shift();
  y = a.splice(0, 3);
  r = a.filter(z => z < x);
  if (!r.length) r = a;
  z = r.reduce((acc, val) => Math.max(acc, val));
  a.splice(a.indexOf(z) + 1, 0, ...y);
  a.push(x);
}
o = a.indexOf(1);
[...a.slice(o + 1), ...a.slice(0, o)].join('')

p23b.js

a = [...document.querySelector('.puzzle-input').textContent].map(x => Number(x));
cups = 1e6;
nxt = [];
for (i = 0; i < a.length - 1; i++) nxt[a[i]] = a[i + 1];
nxt[a[a.length - 1]] = a.length + 1;
for (j = a.length + 1; j < cups; j++) nxt[j] = j + 1;
nxt[cups] = a[0];
for (i = 0, cur = a[0]; i < 1e7; i++, cur = nxt[cur]) {
  p = nxt[cur], q = nxt[p], r = nxt[q];
  t = cur - 1;
  while ([p, q, r].includes(t)) t--;
  if (!t) t = cups;
  nxt[cur] = nxt[r], nxt[r] = nxt[t], nxt[t] = p;
}
nxt[1] * nxt[nxt[1]]

p24a.js

dirs = {e: 1, w: -1, ne: 1000, nw: 999, se: -999, sw: -1000};
document.body.textContent.trim().split('\n')
  .map(x => x.match(new RegExp(Object.keys(dirs).join('|'), 'g')).map(x => dirs[x]).reduce((acc, val) => acc + val))
  .reduce((acc, val) => acc.has(val) ? (acc.delete(val), acc) : acc.add(val), new Set())
  .size

p24b.js

dirs = {e: 1, w: -1, ne: 1000, nw: 999, se: -999, sw: -1000};
a = document.body.textContent.trim().split('\n')
  .map(x => x.match(new RegExp(Object.keys(dirs).join('|'), 'g')).map(x => dirs[x]).reduce((acc, val) => acc + val))
  .reduce((acc, val) => acc.has(val) ? (acc.delete(val), acc) : acc.add(val), new Set());
nbs = x => Object.values(dirs).map(d => x + d);
keep = x => (cnt = nbs(x).filter(x => a.has(x)).length, a.has(x) && cnt === 1 || cnt === 2);
for (t = 0; t < 100; t++) {
  a = new Set([...new Set([...a, ...[...a].flatMap(nbs)])].filter(keep));
}
a.size

p25.js

[a, b] = document.body.textContent.trim().split('\n').map(x => Number(x));
for (loops = 1, c = 7; c != b; loops++, c = c * 7 % 20201227) {}
for (c = 1; loops; loops--) c = c * a % 20201227;
c