Advent of Code 2020 Day 2

day2.ts

import { readFileSync } from 'fs';

type PasswordPolicy = {
    [key: string]: any
}
type OcurrencePasswordPolicy = {
    [key: string]: { min: number, max: number }
}
type PositionPasswordPolicy = {
    [key: string]: number[]
}

type ParsingStrategy<T> = (policy: string) => T;

const parseOcurrencePolicies = (policy: string): OcurrencePasswordPolicy => {
    const [ range, character ] = policy.split(' ');
    const [ min, max ] = range.split('-').map(x => parseInt(x));

    return { [character]: { min, max } };
}

const parsePositionPolicy = (policy: string): PositionPasswordPolicy => {
    const [ positions, character ] = policy.split(' ');
    return { [character]: positions.split('-').map(x => parseInt(x)) };
}

function parsePasswordEntry<T>(str: string, parsingStrategy: ParsingStrategy<T>) {
    const split = str.split(': ');
    return {
        policy: parsingStrategy(split[0]),
        password: split[1]
    };
}

function countOcurrences(str: string, char: string) {
    return new Array(...str).filter(c => c === char).length;
};

const enforceOcurrencePolicy = (password: string, policy: OcurrencePasswordPolicy) => {
    return Object.keys(policy).every(character => {
        const characterPolicy = policy[character];
        const ocurrences = countOcurrences(password, character);
        return ocurrences >= characterPolicy.min && ocurrences <= characterPolicy.max;
    });
}

const enforcePositionPolicy = (password: string, policy: PositionPasswordPolicy) => {
    return Object.keys(policy).every(character => {
        const characterPolicy = policy[character];
        return [
            password[characterPolicy[0] - 1],
            password[characterPolicy[1] - 1]
        ].filter(x => x === character).length === 1;
    });
}

const raw = readFileSync('input.txt').toString('utf8').split('\n');

const chp1Passwords = raw.map(x => parsePasswordEntry(x, parseOcurrencePolicies));
const chp1ValidPasswords = chp1Passwords.filter(pw => enforceOcurrencePolicy(pw.password, pw.policy));
console.log(`chapter 1: ${chp1ValidPasswords.length}`);

const chp2Passwords = raw.map(x => parsePasswordEntry(x, parsePositionPolicy));
const chp2ValidPasswords = chp2Passwords.filter(pw => enforcePositionPolicy(pw.password, pw.policy));
console.log(`chapter 2: ${chp2ValidPasswords.length}`);