aoc-2021/day08/day08.ts

import * as A from "fp-ts/Array";
import * as S from "fp-ts/string";
import * as RA from "fp-ts/ReadonlyArray";
import * as N from "fp-ts/number";
import { flow, pipe } from "fp-ts/lib/function";
import { concatAll } from "fp-ts/lib/Monoid";
import { fromCompare } from "fp-ts/Ord";

import { signalPatterns as testSignalPatterns } from "./input.test";
import { signalPatterns as inputSignalPatterns } from "./input";

type SignalPatterns = {
    patterns: string[],
    digits: string[]
};

const parseSignalPatterns = (input: string) => pipe(
    input.split("\n"),
    A.map(lines => lines.split(" | ")),
    A.map(lineParts => pipe(lineParts, A.map(parts => parts.split(" ")))),
    A.map(([patterns, digits]) => ({ patterns, digits }))
);

const signalPatterns = parseSignalPatterns(
    // testSignalPatterns
    inputSignalPatterns
);

const easyDigitCount = pipe(
    signalPatterns,
    A.map(signalPattern => signalPattern.digits),
    A.flatten,
    A.reduce(0, (count, digit) => pipe([2, 4, 3, 7], A.some(n => n === digit.length)) ? count + 1 : count)
);

console.log(easyDigitCount);

type PatternKey = { [pattern: string]: string };

const deductKey = (patterns: string[]): PatternKey => {
    return pipe(
        patterns,
        A.map(p => pipe(p, S.split(""), RA.sort(S.Ord), concatAll(S.Monoid))),
        A.sort(fromCompare((a: string, b: string) => a.length < b.length ? -1 : a.length > b.length ? 1 : 0)),
        A.reduce({} as PatternKey, (key, pattern) => {
            const segmentsOf = (value: string) => pipe(
                pipe(Object.keys(key), A.filter(k => key[k] === value)),
                A.map(S.split("")),
                RA.flatten
            );
            const contains = (segments: readonly string[]) => (pattern: string) => pipe(
                segments,
                RA.reduce(true, (res, segment) => res && S.includes(segment)(pattern))
            )
            switch ((pipe(pattern, S.size))) {
                case 2:
                    return { ...key, [pattern]: "1" };
                case 3:
                    return { ...key, [pattern]: "7" };
                case 4:
                    return { ...key, [pattern]: "4" };
                case 5:
                    if (pipe(pattern, contains(segmentsOf("1")))) {
                        return { ...key, [pattern]: "3" };
                    }
                    if (pipe(pattern, contains(pipe(segmentsOf("4"), RA.difference(S.Eq)(segmentsOf("1")))))) {
                        return { ...key, [pattern]: "5"};
                    }
                    return { ...key, [pattern]: "2" };
                case 6:
                    if (pipe(pattern, contains(segmentsOf("4")))) {
                        return { ...key, [pattern]: "9" };
                    }
                    if (pipe(pattern, contains(segmentsOf("7")))) {
                        return { ...key, [pattern]: "0" };
                    }
                    return { ...key, [pattern]: "6" };
                case 7:
                    return { ...key, [pattern]: "8" };
                default:
                    return key;
            }
        })
    );
}

const solveDigit = (key: PatternKey) => (digit: string): string => {
    return key[pipe(digit, S.split(""), RA.sort(S.Ord), concatAll(S.Monoid))] ?? "X";
}

const displayDigits = pipe(
    signalPatterns,
    A.map(sp => ({ key: deductKey(sp.patterns), digits: sp.digits })),
    A.map(({ key, digits }) => pipe(digits, A.map(flow(solveDigit(key))))),
    A.map(concatAll(S.Monoid)),
    A.map(parseInt)
);

console.log(pipe(displayDigits, concatAll(N.MonoidSum)));