121 lines
3.1 KiB
TypeScript
121 lines
3.1 KiB
TypeScript
import { Presets, SingleBar } from 'cli-progress';
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import { replaceChar } from '../../utils/array.ts';
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import {
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type Coordinate,
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type Coordinates,
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findCoordsOfDigit,
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getAdjacent,
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inBounds,
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isCoordinateEqual
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} from '../../utils/coordinates.ts';
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export function solveFirst(input: string, minSave = 100): number {
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return solve(input, 2, minSave);
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}
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export function solveSecond(input: string, minSave = 100): number {
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return solve(input, 20, minSave);
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}
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function findPath(
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rows: string[],
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start: Coordinate,
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end: Coordinate
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): Coordinates {
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let [x, y] = start;
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const path: Coordinates = [];
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while (x !== end[0] || y !== end[1]) {
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const last = path.slice(-1)[0] || [-1, -1];
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path.push([x, y]);
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const { top, right, down, left } = getAdjacent(rows, x, y);
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if (top === '.' && last[1] !== y - 1) {
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y--;
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} else if (right === '.' && last[0] !== x + 1) {
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x++;
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} else if (down === '.' && last[1] !== y + 1) {
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y++;
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} else if (left === '.' && last[0] !== x - 1) {
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x--;
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}
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}
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return path;
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}
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function getCheatDirections(maxDistance: number) {
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const cheatDirections: Coordinates = [];
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for (let x = -maxDistance; x <= maxDistance; x++) {
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for (let y = -maxDistance; y <= maxDistance; y++) {
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const d = Math.abs(x) + Math.abs(y);
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if (d > 0 && d <= maxDistance) {
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cheatDirections.push([x, y]);
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}
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}
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}
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return cheatDirections;
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}
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function solve(input: string, maxDistance: number, minSave: number): number {
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const rows = input.split('\n');
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const start = findCoordsOfDigit(rows, 'S')[0];
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const end = findCoordsOfDigit(rows, 'E')[0];
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replaceChar(rows, start[0], start[1], '.');
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replaceChar(rows, end[0], end[1], '.');
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const path = findPath(rows, start, end);
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const totalLength = path.length;
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const cheatDirections = getCheatDirections(maxDistance);
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const isInBounds = inBounds(rows[0].length, rows.length);
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const bar =
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process.env.NODE_ENV === 'test'
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? null
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: new SingleBar({}, Presets.shades_classic);
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bar?.start(totalLength, 0);
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const cheats = path.flatMap((cell, i) => {
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const [x, y] = cell;
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const downgrade = path.slice(0, i + 3);
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const potentialSpots = cheatDirections
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.map(([dx, dy]) => [x + dx, y + dy] as Coordinate)
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.filter(
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(c) =>
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isInBounds(c) &&
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rows[c[1]][c[0]] === '.' &&
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!downgrade.some((d) => isCoordinateEqual(c, d))
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);
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bar?.increment();
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return potentialSpots
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.map((newStart) => {
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const end = path.findIndex((p) => isCoordinateEqual(p, newStart));
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return {
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newStart,
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cell,
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length:
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(end < 0 ? totalLength : end) -
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(i +
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(Math.abs(cell[0] - newStart[0]) +
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Math.abs(cell[1] - newStart[1])))
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};
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})
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.filter((d) => d.length >= minSave);
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});
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bar?.start(cheats.length, 0);
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const existing = new Set<string>();
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for (let cheat of cheats) {
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bar?.increment();
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const key = `${cheat.cell.join(',')}-${cheat.newStart.join(',')}`;
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if (existing.has(key)) {
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continue;
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}
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existing.add(key);
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}
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bar?.stop();
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return existing.size;
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}
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