day19.js

'use strict'

const shuffledArr = arr => {
    const newArr = arr.slice()
    for (let i = newArr.length - 1; i > 0; i--) {
        const rand = Math.floor(Math.random() * (i + 1));
        [newArr[i], newArr[rand]] = [newArr[rand], newArr[i]]
    }
    return newArr
}

const part1 = input => {
    const [recstrings, calstring] = input.trim().split('\n\n')
    const l = calstring.length
    const recs = recstrings.split('\n').reduce((acc, cur) => {
        const [s, r] = cur.split(' => ')
        if (acc.has(s)) {
            acc.set(s, [r].concat(acc.get(s)))
        } else {
            acc.set(s, [r])
        }
        return acc
    }, new Map())
    const cal = [...recs.keys()].reduce((acc, cur) => {
        [...recs.get(cur)].forEach(rep => {
            let p = -1
            do {
                let tmp = ''
                p = calstring.indexOf(cur, p + 1)
                if (p >= 0) {
                    switch(p) {
                        case 0:
                            tmp = rep + calstring.substring(cur.length)
                            break
                        case l - 1:
                            tmp = calstring.substring(0, l - cur.length) + rep
                            break
                        default:
                            tmp = calstring.substring(0, p) + rep + calstring.substring(p + cur.length)
                    }
                    acc.add(tmp)
                }
            } while (p >= 0 && p < l);
        })
        return acc
    }, new Set())
    return cal.size
}

const part2 = input => {
	const [recstrings, calstring] = input.trim().split('\n\n')
	let molecules = shuffledArr(recstrings.split('\n').map(line => line.split(' => ')))
	let tmp = calstring, i = 0, j = 0
	while(tmp !== 'e') {
		for (const [inp, out] of molecules) {
			if (tmp.includes(out)) {
				tmp = tmp.replace(out, inp)
				i++
			}
		}
		if (j == i) {
			tmp = calstring, i = 0, j = 0
			molecules = shuffledArr(molecules)
		} else {
			j = i
		}
	}
	return i
}

module.exports = { part1, part2, shuffledArr }