advent-of-code/2021/3.ts

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import { collectArray, inputLines, measureDuration } from "./common.ts";
const input = await collectArray(await inputLines("3"));
type SubmarineCommand = ["forward", number] | ["up", number] | ["down", number];
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type Counters = [zeroCount: number, oneCount: number][];
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const ASCII_ZERO = "0".charCodeAt(0);
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function countBits(
input: string[],
width?: number,
windowWidth?: number,
): Counters {
if (!width) width = input[0].length;
if (!windowWidth) windowWidth = width;
const counter: Counters = Array.from(Array(width), (_) => [0, 0]);
for (const l of input) {
for (let i = width - windowWidth; i < width; i++) {
const val = l.charCodeAt(i) - ASCII_ZERO;
counter[i][val]++;
}
}
return counter;
}
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export function part1(input: string[]): number {
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const width = input[0].length;
const counter = countBits(input);
const ones = [...Array(width).keys()].reduce((acc, i) =>
acc += (counter[i][1] >= counter[i][0]) ? (1 << i) : 0
);
// xor with a mask the same size as the width to get the zeroes value
console.log("oz:", ones);
return ones * (ones ^ (Math.pow(2, width) - 1));
}
await measureDuration(() => console.log("Part 1", part1(input)));
export function part2(input: string[]): number {
// I hate this.
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const width = input[0].length;
const counter = Array.from(Array(width), (_) => [0, 0]);
for (const l of input) {
for (let i = 0; i < width; i++) {
const val = l.charCodeAt(i) - ASCII_ZERO;
counter[i][val]++;
}
}
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let oxyGenRating = null;
let coScrubRating = null;
let oxyGenCandidates = input.slice(0);
let coScrubCandidates = input.slice(0);
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for (let i = 0; i < width; i++) {
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const newOxyGenCandidates: string[] = [];
const newCoScrubCandidates: string[] = [];
// console.log(counter[i]);
const moreCommon = (counter[i][1] > counter[i][0] ? 1 : 0).toString();
// console.log(i, width, moreCommon);
if (!oxyGenRating) {
for (const binnum of oxyGenCandidates) {
if (binnum[i] == moreCommon) newOxyGenCandidates.push(binnum);
}
if (newOxyGenCandidates.length == 1) {
oxyGenRating = parseInt(newOxyGenCandidates[0], 2);
/*
console.log(
"Oxygen Generator Rating:",
oxyGenRating,
oxyGenCandidates,
newOxyGenCandidates,
);
*/
} else oxyGenCandidates = newOxyGenCandidates;
// console.log(oxyGenCandidates);
}
if (!coScrubRating) {
for (const binnum of coScrubCandidates) {
if (binnum[i] != moreCommon) newCoScrubCandidates.push(binnum);
}
if (newCoScrubCandidates.length == 1) {
coScrubRating = parseInt(newCoScrubCandidates[0], 2);
/*
console.log(
"CO2 Scrubber Rating:",
coScrubRating,
coScrubCandidates,
newCoScrubCandidates,
);
*/
} else coScrubCandidates = newCoScrubCandidates;
// console.log(coScrubCandidates);
}
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}
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return (oxyGenRating || 0) * (coScrubRating || 0);
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}
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// await measureDuration(() => console.log("Part 2", part2(input)));