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day16.js
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day16.js
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const { data, test } = require('./data/day16');
const hexToBin = (hex) => (parseInt(hex, 16).toString(2)).padStart(4, '0');
const parseInput = ([input]) => (
input.split('').reduce((agg, curr) => [...agg, ...hexToBin(curr).split('')], [])
);
const HEADER_BITS = 6;
const processLiteralRest = (rest, processExtraBits = true) => {
let next = [...rest];
let value = [];
let readNext, c1, c2, c3, c4;
do {
([readNext, c1, c2, c3, c4, ...next] = next);
value = [...value, c1, c2, c3, c4];
} while(readNext !== '0');
const valueLen = value.length;
const currentTotalLength = valueLen + (valueLen / 4);
let skip = [];
if (processExtraBits) {
const skipBits = 8 - ((currentTotalLength + HEADER_BITS) % 8);
skip = next.slice(0, skipBits);
next = next.slice(skipBits);
}
const processedLength = currentTotalLength + skip.length;
return { value: parseInt(value.join(''), 2), skip, processedLength, remaining: next };
};
const processOperator = (rest) => {
let [lengthType, ...next] = [...rest];
let lengthSubPackets;
let numSubPackets;
if (lengthType === '0') {
// next 15 = total length of subpackets of this operator
lengthSubPackets = parseInt(next.slice(0, 15).join(''), 2);
next = next.slice(15);
} else {
// next 11 = total number of subpackets of this operator
numSubPackets = parseInt(next.slice(0, 11).join(''), 2);
next = next.slice(11);
}
const value = [];
let childProcessedLength = 0;
let version, type, elValue, processedLength, skip, remaining;
if (lengthType === '0') {
while (childProcessedLength < lengthSubPackets) {
({
version,
type,
value: elValue,
processedLength,
skip,
remaining,
} = processNextPacket(next));
value.push({
version,
type,
value: elValue,
processedLength,
});
next = remaining;
childProcessedLength += processedLength;
}
const totalProcessedLength = value.reduce((len, curr) => len + curr.processedLength, 0) + 1 + 15;
return { value, skip, processedLength: totalProcessedLength, remaining };
}
for (let i = 0; i < numSubPackets; i++) {
({
version,
type,
value: elValue,
processedLength,
skip,
remaining,
} = processNextPacket(next));
value.push({
version,
type,
value: elValue,
processedLength,
});
next = remaining;
childProcessedLength += processedLength;
}
const totalProcessedLength = value.reduce((len, curr) => len + curr.processedLength, 0) + 1 + 11;
return { value, skip, processedLength: totalProcessedLength, remaining };
};
const processNextPacket = (input, shouldSkipToEnd = false) => {
const [v1, v2, v3, t1, t2, t3, ...rest] = input;
const vBin = [v1, v2, v3].join('');
const tBin = [t1, t2, t3].join('');
const version = parseInt(vBin, 2);
const type = parseInt(tBin, 2);
let value;
let remaining;
let skip;
let processedLength;
if (type === 4) {
({ value, skip, processedLength, remaining } = processLiteralRest(rest, shouldSkipToEnd));
} else {
({ value, skip, processedLength, remaining } = processOperator(rest));
}
const packetProcessedLength = HEADER_BITS + processedLength;
return {
version,
type,
value,
processedLength: packetProcessedLength,
skip,
remaining,
};
};
const sumVersions = (processedPackets) => {
const sum = JSON.stringify(processedPackets, null, 2)
.split('\n')
.filter(str => str.includes('version'))
.map(str => str.replace(/\s+"version":\s/, ''))
.map(str => str.replace(',', ''))
.map(Number)
.reduce((sum, x) => sum + x, 0);
return sum;
};
const processParsedPacket = ({ version, value, type }) => {
if (type === 0) {
return value.reduce((sum, val) => sum + processParsedPacket(val), 0);
}
if (type === 1) {
return value.reduce((prod, val) => prod * processParsedPacket(val), 1);
}
if (type === 2) {
return Math.min(...value.map(processParsedPacket));
}
if (type === 3) {
return Math.max(...value.map(processParsedPacket));
}
if (type === 4) {
return value;
}
if (type === 5) {
const [first, second] = value;
return processParsedPacket(first) > processParsedPacket(second) ? 1 : 0;
}
if (type === 6) {
const [first, second] = value;
return processParsedPacket(first) < processParsedPacket(second) ? 1 : 0;
}
if (type === 7) {
const [first, second] = value;
return processParsedPacket(first) === processParsedPacket(second) ? 1 : 0;
}
};
console.log(sumVersions(processNextPacket(parseInput(data))));
console.log(processParsedPacket(processNextPacket(parseInput(data))));