advent of code 2023 day 13: part II: vertical reflection

2023/13/impl.js

@@ -1,27 +1,34 @@
 
-const toPatternNotes = (pattern) => {
-	const isPerfectHorizontalReflection = (index) => {
-		let mirrored = true
-		let i = index - 1, j = index + 2
-		while(mirrored && i >= 0 && j < pattern.length) {
-			mirrored = pattern[i] === pattern[j]
-			i -= 1
-			j += 1
+const toPatternNotes = (thePattern) => {
+	const findHorizontalMirror = (pattern, multiplier) => {
+		const isPerfectHorizontalReflection = (index) => {
+			let mirrored = true
+			let i = index - 1, j = index + 2
+			while(mirrored && i >= 0 && j < pattern.length) {
+				mirrored = pattern[i] === pattern[j]
+				i -= 1
+				j += 1
+			}
+			return mirrored
 		}
-		return mirrored
-	}
-	const findHorizontalMirror = () => {
+
 		for(let i = 1; i < pattern.length; i++) {
 			if(pattern[i - 1] === pattern[i] && isPerfectHorizontalReflection(i - 1)) {
-				return i * 100
+				return i * multiplier
 			}
 		}
 		return -1
 	}
-	const findVerticalMirror = () => {
-
+	const findVerticalMirror = (pattern, multiplier) => {
+		// 'Cheat' by finding the horizontal one by rotating 90 degrees
+		const matrix = pattern.map(line => line.split(''))
+		const rotated = matrix[0]
+			.map((val, index) => matrix.map(row => row[index]).reverse())
+			.map(arr => arr.join(''))
+		return findHorizontalMirror(rotated, multiplier)
 	}
-	return findHorizontalMirror()
+	const horizFound = findHorizontalMirror(thePattern, 100)
+	return horizFound != -1 ? horizFound : findVerticalMirror(thePattern, 1)
 }
 
 const solve = (input) => {
@@ -33,4 +40,4 @@ const solve = (input) => {
 
 module.exports = {
 	solve
-}
+}

2023/13/test.js

@@ -4,6 +4,18 @@ const { readFileSync } = require('fs')
 const { solve } = require('./impl.js')
 
 
+test('The reflection notes for vertical reflection is the number of columns to its left', (t) => {
+	const input = `#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.`
+
+	assert.equal(5, solve(input))
+})
+
 test('The reflection notes for horizontal reflection is the number of rows above it multiplied by 100', (t) => {
 const input = `#...##..#
 #....#..#
@@ -16,19 +28,6 @@ const input = `#...##..#
 	assert.equal(400, solve(input))
 })
 
-/*
-test('The reflection notes for vertical reflection is the number of columns to its left', (t) => {
-	const input = `#.##..##.
-..#.##.#.
-##......#
-##......#
-..#.##.#.
-..##..##.
-#.#.##.#.`
-
-	assert.equal(5, solve(input))
-})
-
 test('The sum of the reflection notes in the assignment is 405', (t) => {
 	const input = `#.##..##.
 ..#.##.#.
@@ -48,4 +47,3 @@ test('The sum of the reflection notes in the assignment is 405', (t) => {
 
 	assert.equal(405, solve(input))
 })
-*/