[2024] Solution for Day 19

Author: kfarnung

2024/day19/main.go

@@ -0,0 +1,111 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strings"
+
+	"github.com/kfarnung/advent-of-code/2024/lib"
+)
+
+func part1(input string) int64 {
+	towels, patterns := parseInput(input)
+	count := int64(0)
+
+	for _, pattern := range patterns {
+		if isValidPattern(towels, pattern) {
+			count++
+		}
+	}
+
+	return count
+}
+
+func part2(input string) int64 {
+	towels, patterns := parseInput(input)
+	memo := make(map[string]int64)
+	count := int64(0)
+
+	for _, pattern := range patterns {
+		count += countValidPatterns(towels, pattern, memo)
+	}
+
+	return count
+}
+
+func isValidPattern(towels []string, pattern string) bool {
+	if pattern == "" {
+		return true
+	}
+
+	for _, towel := range towels {
+		if len(towel) > len(pattern) {
+			continue
+		}
+
+		if strings.HasPrefix(pattern, towel) {
+			if isValidPattern(towels, pattern[len(towel):]) {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+func countValidPatterns(towels []string, pattern string, memo map[string]int64) int64 {
+	if pattern == "" {
+		return 1
+	}
+
+	if count, ok := memo[pattern]; ok {
+		return count
+	}
+
+	count := int64(0)
+
+	for _, towel := range towels {
+		if len(towel) > len(pattern) {
+			continue
+		}
+
+		if strings.HasPrefix(pattern, towel) {
+			nextPattern := pattern[len(towel):]
+			tempCount := countValidPatterns(towels, nextPattern, memo)
+			memo[nextPattern] = tempCount
+			count += tempCount
+		}
+	}
+
+	return count
+}
+
+func parseInput(input string) ([]string, []string) {
+	var towels []string
+	var patterns []string
+	for _, line := range lib.SplitLines(input) {
+		if line == "" {
+			continue
+		}
+
+		if towels == nil {
+			towels = strings.Split(line, ", ")
+		} else {
+			patterns = append(patterns, line)
+		}
+	}
+
+	return towels, patterns
+}
+
+func main() {
+	name := os.Args[1]
+	content, err := lib.LoadFileContent(name)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("Part 1: %d\n", part1(content))
+	fmt.Printf("Part 2: %d\n", part2(content))
+}

2024/day19/main_test.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/kfarnung/advent-of-code/2024/lib"
+	"github.com/stretchr/testify/assert"
+)
+
+var input = strings.Join([]string{
+	"r, wr, b, g, bwu, rb, gb, br",
+	"",
+	"brwrr",
+	"bggr",
+	"gbbr",
+	"rrbgbr",
+	"ubwu",
+	"bwurrg",
+	"brgr",
+	"bbrgwb",
+	"",
+}, "\n")
+
+func TestPart1(t *testing.T) {
+	assert.Equal(t, int64(6), part1(input))
+
+	inputContent, err := lib.GetInputContent()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, int64(236), part1(inputContent))
+}
+
+func TestPart2(t *testing.T) {
+	assert.Equal(t, int64(16), part2(input))
+
+	inputContent, err := lib.GetInputContent()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, int64(643685981770598), part2(inputContent))
+}