73 lines
1.5 KiB
JavaScript
73 lines
1.5 KiB
JavaScript
import fs from "fs";
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const TREE = "#";
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const FREE = ".";
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class Grid {
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/**
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* Construct a new Grid from an array of lines
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*
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* @param {string[]} lines The lines of the repeating Grid.
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*/
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constructor(lines) {
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this.lines = lines;
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}
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/**
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* Get the field at the respective coordinate in the grid.
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*
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* @param {number} x X-Coordinate of the field to get.
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* @param {number} y Y-Coordinate of the field to get.
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*
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* @returns {string} The field at the coordinate.
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*/
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get(x, y) {
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if (y > this.lines.length)
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throw new Error(`Out of range [${[x, y]}] max y ${this.lines.length}`);
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const line = this.lines[y];
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return line[x % line.length];
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}
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}
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/**
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* Main function for Puzzle B
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*
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* @param {string} data - Puzzle input as a single string.
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* @returns {number} The number of trees on all slopes, multiplied.
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*/
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async function main(data) {
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const grid = new Grid(data.split("\n").map((line) => line.trim()));
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const slopes = [
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[1, 1],
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[3, 1],
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[5, 1],
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[7, 1],
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[1, 2],
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];
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let result = 1;
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for (const slope of slopes) {
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const [dX, dY] = slope;
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let x = 0;
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let y = 0;
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let trees = 0;
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while (y < grid.lines.length) {
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if (grid.get(x, y) === TREE) {
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trees++;
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}
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x += dX;
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y += dY;
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}
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result *= trees;
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}
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return result;
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}
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fs.readFile("input", (err, data) => {
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if (err) throw err;
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main(data.toString()).then(console.log).catch(console.error);
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});
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