Add solution day 19 part 2

Author: terminalnode

README.md

@@ -51,7 +51,7 @@ automatically rebuilt and redeployed every time the `common` module or their own
 | 03  | ⭐ ⭐      | 16  | ⭐ 🥸     |
 | 04  | ⭐ ⭐      | 17  | ⭐ ⭐      |
 | 05  | ⭐ ⭐      | 18  | ⭐ ⭐      |
-| 06  | ⭐ ⭐      | 19  | ⭐        |
+| 06  | ⭐ ⭐      | 19  | ⭐ ⭐      |
 | 07  | ⭐ ⭐      | 20  |          |
 | 08  | ⭐ ⭐      | 21  |          |
 | 09  | ⭐ ⭐      | 22  |          |

solutions/day19/main.go

@@ -8,7 +8,7 @@ import (
 )
 
 func main() {
-	common.Setup(19, part1, nil)
+	common.Setup(19, part1, part2)
 }
 
 func part1(
@@ -31,3 +31,50 @@ func part1(
 
 	return fmt.Sprintf("%d of the %d desired designs are possible", count, len(p.desired))
 }
+
+func part2(
+	input string,
+) string {
+	p, err := parse(input)
+	if err != nil {
+		return fmt.Sprintf("Failed to parse input: %v", err)
+	}
+
+	cache := make(map[string]int)
+	count := 0
+	for _, desired := range p.desired {
+		n := loop(p.available, desired, cache)
+		count += n
+	}
+
+	return fmt.Sprintf("Number of available combinations: %d", count)
+}
+
+func loop(
+	available []string,
+	target string,
+	cache map[string]int,
+) int {
+	cacheValue, isCached := cache[target]
+	if isCached {
+		return cacheValue
+	}
+
+	l := len(target)
+	sum := 0
+	for _, pattern := range available {
+		pl := len(pattern)
+		if pl > l {
+			continue
+		}
+
+		if pattern == target {
+			sum += 1
+		} else if target[:pl] == pattern {
+			sum += loop(available, target[pl:], cache)
+		}
+	}
+
+	cache[target] = sum
+	return sum
+}