advent of code 2023 day 11: test galaxy expanding separately, fix rest

2023/11/impl.js

@@ -1,41 +1,49 @@
 
-module.exports.solve = function(input) {
-	const expandGalaxyInDepth = (map) => {
-		[...Array(map.length).keys()].forEach(rownr => {
-			if(new Set(map[rownr]).size === 1 && map[rownr][0] === '.') {
-				map.splice(rownr, 0, '.'.repeat(map[0].length).split(''))
-			}
+const expandGalaxyInDepth = (map) => {
+	[...Array(map.length).keys()]
+		.filter(rownr => new Set(map[rownr]).size === 1 && map[rownr][0] === '.')
+		.forEach((rownr, i) => {
+			// Don't do this in a forEach() over the rows! What a mistaka to-a maka...
+			map.splice(rownr + i, 0, '.'.repeat(map[rownr].length).split(''))
 		})
-		return map
-	}
-	const expandGalaxyInBreadth = (map) => {
-		const rownrs = [...Array(map.length).keys()];
-		[...Array(map[0].length).keys()]
-			.filter(colnr => new Set(rownrs.map(rownr => map[rownr][colnr])).size === 1 && map[0][colnr] === '.')
-			.forEach(colnr => {
-			rownrs.forEach(rownr => {
-				map[rownr].splice(colnr, 0, '.')	// There's something not quite right about this?
-			})	
+	return map
+}
+const expandGalaxyInBreadth = (map) => {
+	const rownrs = [...Array(map.length).keys()];
+	[...Array(map[0].length).keys()]
+		.filter(colnr => new Set(rownrs.map(rownr => map[rownr][colnr])).size === 1 && map[0][colnr] === '.')
+		.reverse()
+		.forEach(colnr => {
+		rownrs.forEach(rownr => {
+			map[rownr].splice(colnr, 0, '.')
 		})
-		return map
-	}
-	const discoverGalaxy = (map) => {
-		const galaxies = []
-		// Trying to create these loops functionally here seems to work against me in JS
-		for(let i = 0; i < map.length; i++) {
-			for(let j = 0; j < map[i].length; j++) {
-				if(map[i][j] === '#') {
-					galaxies.push([i, j])
-				}
+	})
+	return map
+}
+const expandGalaxy = (map) => expandGalaxyInDepth(expandGalaxyInBreadth(map))
+const discoverGalaxy = (map) => {
+	const galaxies = []
+	// Trying to create these loops functionally here seems to work against me in JS
+	for(let i = 0; i < map.length; i++) {
+		for(let j = 0; j < map[i].length; j++) {
+			if(map[i][j] === '#') {
+				galaxies.push([i, j])
 			}
 		}
-		return galaxies
 	}
+	return galaxies
+}
 
-	const map = expandGalaxyInBreadth(expandGalaxyInDepth(input.split('\n').map(row => row.split(''))))
+const solve = (input) => {
+	const map = expandGalaxy(input.split('\n').map(row => row.split('')))
 	const planets = discoverGalaxy(map)
 	return planets
 		// Cutting corners: difference in coords = minimum distance. Won't always work?
 		.flatMap((v, i) => planets.slice(i+1).map(w => Math.abs(v[0] - w[0]) + Math.abs(v[1] - w[1])))
 		.reduce((a, b) => a + b)
 }
+
+module.exports = {
+	expandGalaxy,
+	solve
+}

2023/11/test.js

@@ -1,9 +1,50 @@
 const test = require('node:test')
 const assert = require('node:assert').strict;
 const { readFileSync } = require('fs')
-const { solve } = require('./impl.js')
+const { expandGalaxy, solve } = require('./impl.js')
+
+const toMap = (input) => input.split('\n').map(row => row.split(''))
+const fromMap = (map) => {
+	let str = ""
+	for(let i = 0; i < map.length; i++) {
+		for(let j = 0; j < map[i].length; j++) {
+			str += map[i][j]
+		}
+		str += '\n'
+	}
+	return str
+}
+
+test('Expanding the galaxy works as expected', (t) => {
+	const map = `...#......
+.......#..
+#.........
+..........
+......#...
+.#........
+.........#
+..........
+.......#..
+#...#.....`
+	const expanded = `....#........
+.........#...
+#............
+.............
+.............
+........#....
+.#...........
+............#
+.............
+.............
+.........#...
+#....#.......
+`
+
+	const actual = fromMap(expandGalaxy(toMap(map)))
+	assert.equal(expanded, actual)
+})
+
 
-/*
 test('The single shortest path in an isolated example is 9', (t) => {
 	const input = `...x......
 .......x..
@@ -18,7 +59,7 @@ x...#.....`
 
 	assert.equal(9, solve(input))	
 })
-*/
+
 
 test('The sum of the shortest paths between galaxies in the assignment is 374', (t) => {
 	const input = `...#......