Advent of Code: 2021 Day 14 / Jo Wood

Jo Wood

Professor of Visual Analytics interested in design, geovisualization, visual storytelling and computational thinking.

Workspace

Public

Ξ🎄Advent of Code 2021

Edited

Sep 17, 2023

function parse(input) {

const rules = new Map();

input.rules.forEach((r) => rules.set(...r.split(" -> ")));

return rules;

}

function pairFreqs(input, numIterations) {

const rules = parse(input);

const pairs = d3.pairs(input.template, (a, b) => a + b);

let freqsPrev = pairs.reduce((e, v) => AOC.addToFreqTable(e, v), new Map());

for (let i = 0; i < numIterations; i++) {

const freqs = new Map();

for (const [pair, f] of freqsPrev.entries()) {

const [a, b] = pair.split("");

const c = rules.get(pair);

[a + c, c + b].forEach((p) => AOC.addToFreqTable(freqs, p, f));

}

freqsPrev = freqs;

}

return freqsPrev;

}

function freqOf(elem, freqs, input) {

return (

(elem === input.template[input.template.length - 1] ? 1 : 0) +

[...freqs.entries()].reduce(

(total, [pair, f]) => (pair.split("")[0] === elem ? total + f : total),

)

);

}

function calcRange(input, numIterations) {

const pairTable = pairFreqs(input, numIterations);

const elemFreqs = [...new Set(parse(input).values())].map((elem) =>

freqOf(elem, pairTable, input)

);

return Math.max(...elemFreqs) - Math.min(...elemFreqs);

}

function part1(input) {

return calcRange(input, 10);

}

function part2(input) {

return calcRange(input, 40);

}

test1 = ({ template: test1a, rules: test1b })

test1a = `NNCB`.split("")

puzzleInput = ({ template: puzzleInputA, rules: puzzleInputB })

puzzleInputA = `OHFNNCKCVOBHSSHONBNF`.split("")

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