Tinkering with code and algorithms for fun
input_text = (await FileAttachment(
"Avent of Code 2020 - Day 19.txt"
).text()).trim()
function parseInput(input) {
let [rulesArr, messages] = input.split('\n\n').map(txt => txt.split('\n'));
const rulesArr2 = [];
for (let rule of rulesArr) {
let [nr, match] = rule.split(': ');
nr |= 0;
match = match
.split(' | ')
.map(rulePart =>
rulePart
.split(' ')
.map(nr => (+nr + "" === nr ? +nr : nr.slice(1, nr.length - 1)))
);
const isString = typeof match[0][0] === "string";
const pair = [
nr,
{
isString,
match: isString ? match[0] : match
}
];
rulesArr2.push(pair);
}
// sort by rule nr
rulesArr2.sort((a, b) => a[0] - b[0]);
const rules = new Map();
const stringRules = new Map(); // rules that don't refer to other rules
for (const [nr, rule] of rulesArr2) {
rules.set(nr, rule);
if (rule.isString) stringRules.set(nr, rule);
}
return { rules, stringRules, messages };
}
input = parseInput(input_text)
flattenRules(testInput)
/*
If you uncomment the next cells, it turns out there are 2097152 possible strings that match rule 0
Intersect that with the messages in the input and you get 220 matches.
Output looks like this:
answer1 = Object {
flatRules: Object {passes: 10, flattened: Map(138)}
matchesRule0: Array(220) ["aaabbaabbaaababaaaaabbbb", "babaaaabaabbbababbbabaaa", "abbaabaabaaabababaaababb", "bbbabbaabbaababbabaaabaa", "bbaabaababbbaababbbbaaab", "baaaababaababbbbabbbabab", "bbaabbbaaaaabaabbabababb", "abababbaabbaabaaababbbbb", "abbbabbaabbbaabaaaabaaab", "ababbbaaaababaabbaaaabbb", "abbbbaabaaaababbbbbbaaaa", "bbbababababaabababaaaaab", "aabababaabbababbaabbbaaa", "abbaababbabbbbabbbbabbab", "baaabbababbbbbabaabbbabb", "aabaabbbbaabaababaababaa", "bbaabaaabbbbbbaaabababaa", "bbaabbabaaaaababbbbbabab", "abbabbababaabbabbaaabbba", "babaaabbabbaaaabbaabaabb", …]
time: 2486
}
(commented out because sloooow)
*/
// answer1 = {
// const t0 = performance.now();
// const flatRules = flattenRules(input);
// const rule0 = new Set(flatRules.flattened.get(0).match);
// let matchesRule0 = [];
// for (const msg of input.messages) {
// if (rule0.has(msg)) matchesRule0.push(msg);
// }
// return { flatRules, matchesRule0, time: performance.now() - t0 };
// }
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