updates

2024/go/day19/day19.go

@@ -0,0 +1,87 @@
+package day19
+
+import (
+	"sort"
+	"strings"
+)
+
+func Part1(input string) int {
+	in := strings.Split(input, "\n\n")
+	towels := strings.Split(in[0], ", ")
+	patterns := strings.Split(in[1], "\n")
+	//	fmt.Println(towels, patterns)
+	count := 0
+	not_possibles := make(map[string]bool)
+	for _, pattern := range patterns {
+		if isPossible(towels, pattern, not_possibles) {
+			//			fmt.Println(count, pattern)
+			count++
+		}
+	}
+	return count
+}
+
+func Part2(input string) int {
+	in := strings.Split(input, "\n\n")
+	towels := strings.Split(in[0], ", ")
+	sort.Strings(towels)
+	patterns := strings.Split(in[1], "\n")
+	//	fmt.Println(towels, patterns)
+	count := 0
+	memo := make(map[string]int)
+	for _, pattern := range patterns {
+		count += countPossible(sortStringsByPrefix(towels), pattern, memo)
+	}
+	return count
+}
+
+func isPossible(towels []string, pattern string, not_possibles map[string]bool) bool {
+	if pattern == "" {
+		return true
+	}
+	if not_possibles[pattern] {
+		return false
+	}
+	for _, towel := range towels {
+		if strings.HasPrefix(pattern, towel) {
+			if isPossible(towels, pattern[len(towel):], not_possibles) {
+				return true
+			}
+		}
+	}
+	not_possibles[pattern] = true
+	return false
+}
+
+func countPossible(towels map[byte][]string, pattern string, memo map[string]int) int {
+	if pattern == "" {
+		return 1
+	}
+
+	//If memo has key
+	if val, ok := memo[pattern]; ok {
+		return val
+	}
+
+	count := 0
+	for _, towel := range towels[pattern[0]] {
+		if strings.HasPrefix(pattern, towel) {
+			count += countPossible(towels, pattern[len(towel):], memo)
+		}
+	}
+
+	memo[pattern] = count
+
+	return count
+}
+
+func sortStringsByPrefix(slice []string) map[byte][]string {
+	result := make(map[byte][]string)
+	for _, str := range slice {
+			result[str[0]] = append(result[str[0]], str)
+		}
+	for _, t := range result {
+		sort.Strings(t)
+	}
+	return result
+}