new version without ugly parser :)

digidis-go/day25/day25.go

@@ -2,65 +2,40 @@ package main
 
 import (
 	"fmt"
-	"io/ioutil"
-	"strconv"
-	"strings"
 )
 
 type rule struct {
-	v bool
+	v int
 	p int
 	n string
 }
 
 func main() {
+	rules := map[string][2]rule{
+		"F": [2]rule{rule{0, 1, "C"}, rule{0, 1, "E"}},
+		"A": [2]rule{rule{1, 1, "B"}, rule{0, -1, "D"}},
+		"B": [2]rule{rule{1, 1, "C"}, rule{0, 1, "F"}},
+		"C": [2]rule{rule{1, -1, "C"}, rule{1, -1, "A"}},
+		"D": [2]rule{rule{0, -1, "E"}, rule{1, 1, "A"}},
+		"E": [2]rule{rule{1, -1, "A"}, rule{0, 1, "B"}},
+	}
+
+	s := "A"
+	steps := 12302209
 
-	s, c, rules := parse()
 	var pos, checksum int
-	v := make(map[int]bool)
+	v := make(map[int]int)
 
-	for ; c > 0; c-- {
+	for c := 0; c < steps; c++ {
 		i := v[pos]
 		v[pos] = rules[s][i].v
 		pos += rules[s][i].p
 		s = rules[s][i].n
 	}
 
-	for i := range v {
-		if v[i] {
-			checksum++
-		}
+	for _, i := range v {
+		checksum += i
 	}
 
 	fmt.Printf("Checksum: %v\n", checksum)
 }
-
-func parse() (string, int, map[string]map[bool]rule) {
-	data, _ := ioutil.ReadFile("input.txt")
-	parts := strings.Split(string(data), "\n\n")
-
-	rules := make(map[string]map[bool]rule)
-
-	rows := strings.Split(parts[0], "\n")
-	steps, _ := strconv.Atoi(strings.Fields(rows[1])[5])
-	state := strings.TrimSuffix(strings.Fields(rows[0])[3], ".")
-
-	for _, p := range parts[1:] {
-		rows := strings.Split(p, "\n")
-		s := strings.TrimSuffix(strings.Fields(rows[0])[2], ":")
-		rules[s] = map[bool]rule{false: getRule(rows[1:]), true: getRule(rows[5:])}
-	}
-
-	return state, steps, rules
-}
-
-func getRule(f []string) rule {
-	v := strings.HasSuffix(f[1], "1.")
-	p := -1
-	if strings.HasSuffix(f[2], "right.") {
-		p = 1
-	}
-	nf := strings.Fields(f[3])
-	n := strings.TrimSuffix(nf[len(nf)-1], ".")
-	return rule{v, p, n}
-}