84 lines
2.1 KiB
JavaScript
84 lines
2.1 KiB
JavaScript
import fp from "lodash/fp.js";
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import _ from "lodash";
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import * as p1 from "./part1.mjs";
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function decodedDigits(mapping) {
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const s = fp.invert(mapping);
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return _.flow([
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fp.invert,
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fp.mapKeys((k) =>
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k
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.split("")
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.map((l) => s[l])
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.join("")
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),
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fp.mapKeys((k) => k.split("").sort().join("")),
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])(p1.digits);
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}
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function guess(unknowns, guessed = {}, inputs) {
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const [next] = Object.keys(unknowns);
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if (!next) return guessed;
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for (const p of unknowns[next]) {
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let newUnknowns = fp.mapValues(
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(s) => s.filter((x) => x !== p),
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fp.omit(next, unknowns)
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);
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if (Object.values(newUnknowns).some((s) => s.size === 0)) continue;
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const r = guess(newUnknowns, { ...guessed, [next]: p }, inputs);
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if (!r) continue;
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const solution = decodedDigits(r);
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if (inputs.every((i) => solution.hasOwnProperty(i.join(""))))
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return r;
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}
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}
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export function findMapping(input) {
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const values = "abcdefg".split("");
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let possibility = Object.fromEntries(values.map((v) => [v, values]));
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for (const seq of input) {
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const p = Object.values(p1.digits)
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.filter((d) => d.length === seq.length)
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.join("")
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.split("");
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for (const l of seq) {
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possibility[l] = _.intersection(possibility[l], p);
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}
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}
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// feel cute, might delete later
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const one = input.find((i) => i.length === 2);
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const seven = input.find((i) => i.length === 3);
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const [a] = seven.filter((x) => !one.includes(x));
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possibility = fp.mapValues(fp.reject("a"), possibility);
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possibility[a] = ["a"];
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return guess(possibility, {}, input);
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}
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export function decodedOutput({ input, output }) {
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const mapping = findMapping([...input, ...output]);
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const digits = decodedDigits(mapping);
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return parseInt(output.map((e) => digits[e.join("")]).join(""));
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}
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export function solution(input) {
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return _.sum(input.map(decodedOutput));
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}
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