add day19; to slow to solve part2

day19/rearrangements.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+    "fmt"
+    "strings"
+    "os"
+)
+
+func count(pattern string, towels []string) int {
+    counter := 0
+
+	// Iterate over the map in sorted key order
+	for _, t := range towels {
+        if pattern == t { counter++ }
+
+        if strings.HasPrefix(pattern, t) {
+            counter += count(pattern[len(t):], towels)
+        }
+    }
+
+    return counter
+}
+
+func count_with_map(pattern string, pmap map[string]int) int {
+    counter := 0
+    
+	for key, val := range pmap {
+        if pattern == key { return val }
+
+        if strings.HasPrefix(pattern, key) {
+            counter += count_with_map(pattern[len(key):], pmap)
+        }
+    }
+
+    return counter
+}
+
+func construct_pmap(towels []string) map[string]int {
+    pmap := make(map[string]int)
+
+    for _, t := range towels {
+        pmap[t] = count(t, towels)
+    }
+    
+    return pmap
+}
+
+func check(err error) {
+    if err != nil { panic(err) }
+}
+
+func main() {
+    dat, err := os.ReadFile("data.txt")
+    check(err)
+    input := strings.TrimSpace(string(dat))
+    
+    towels   := strings.Split(strings.Split(input, "\n\n")[0], ", ")
+    patterns := strings.Split(input, "\n\n")[1]
+
+    // maps pattern to number of combinations
+    pmap := construct_pmap(towels)
+
+    counter := 0
+    for i, pattern := range strings.Split(patterns, "\n") {
+        counter += count_with_map(pattern, pmap)
+    }
+
+    fmt.Println(counter)
+}