day nineteen checkpoint. Doesn't work yet.

19/main.go

@@ -0,0 +1,175 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func main() {
+	start := time.Now()
+	partOne()
+	duration := time.Since(start)
+	partTwo()
+	duration2 := time.Since(start)
+	fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
+}
+
+// options: 20 => [][20]; 20 10 => [][20, 10]; 20 | 10 => [][20][10]; 20 10 | 39 12 => [][20, 10][39, 12];
+// token is only set for the two "bottom" rules of "a" and "b"
+// options and token will never both be set
+// ints all point to rule numbers in overall rule list
+type rule struct {
+	name    int
+	options [][]int
+	token   rune
+}
+
+func parseRule(s string) rule {
+	r := rule{
+		options: make([][]int, 0),
+	}
+	sp := strings.Split(s, ": ")
+	r.name, _ = strconv.Atoi(sp[0])
+
+	// either it's a token rule...
+	if sp[1] == `"a"` || sp[1] == `"b"` {
+		r.token = []rune(strings.Trim(sp[1], `"`))[0]
+		return r
+	}
+
+	// ...or an options rule.
+	opts := strings.Split(sp[1], " | ")
+	for _, o := range opts {
+		opt := []int{}
+		for _, i := range strings.Split(o, " ") {
+			ii, _ := strconv.Atoi(i)
+			opt = append(opt, ii)
+		}
+		r.options = append(r.options, opt)
+	}
+	return r
+}
+
+func validateString(rules []rule, currentRule int, s string) (bool, string) {
+	activeRule := rules[currentRule]
+	// if we're run out of string, the rule obviously cannot match
+	if len(s) == 0 {
+		return false, ""
+	}
+	// we've reached a leaf; check if the current head of the string matches our expected rune
+	if len(activeRule.options) == 0 {
+		return []rune(s)[0] == activeRule.token, s[1:]
+	}
+	// if there's only one option, attempt to apply the rules
+	if len(activeRule.options) == 1 {
+		option := activeRule.options[0]
+		if len(option) == 1 {
+			return validateString(rules, option[0], s)
+		}
+		if len(option) == 2 {
+			ok, remainder := validateString(rules, option[0], s)
+			if ok {
+				return validateString(rules, option[1], remainder)
+			}
+		}
+		if len(option) == 3 {
+			ok, remainder := validateString(rules, option[0], s)
+			if ok {
+				ok, remainder = validateString(rules, option[1], remainder)
+			}
+			if ok {
+				return validateString(rules, option[2], remainder)
+			}
+		}
+	}
+	// otherwise, we need to branch into our options and try and apply their rules
+	if len(activeRule.options) == 2 {
+		ok := false
+		remainder := ""
+		optionOne := activeRule.options[0]
+		if len(optionOne) == 1 {
+			ok, remainder = validateString(rules, optionOne[0], s)
+		}
+		if len(optionOne) == 2 {
+			ok, remainder = validateString(rules, optionOne[0], s)
+			if ok {
+				ok, remainder = validateString(rules, optionOne[1], remainder)
+			}
+		}
+		if len(optionOne) == 3 {
+			ok, remainder = validateString(rules, optionOne[0], s)
+			if ok {
+				ok, remainder = validateString(rules, optionOne[1], remainder)
+			}
+			if ok {
+				ok, remainder = validateString(rules, optionOne[2], remainder)
+			}
+		}
+		if ok {
+			return ok, remainder
+		}
+		optionTwo := activeRule.options[1]
+		if len(optionTwo) == 1 {
+			ok, _ = validateString(rules, optionTwo[0], s)
+		}
+		if len(optionTwo) == 2 {
+			ok, remainder = validateString(rules, optionTwo[0], s)
+			if ok {
+				return validateString(rules, optionTwo[1], remainder)
+			}
+		}
+		if len(optionTwo) == 3 {
+			ok, remainder = validateString(rules, optionTwo[0], s)
+			if ok {
+				ok, remainder = validateString(rules, optionTwo[1], remainder)
+			}
+			if ok {
+				return validateString(rules, optionTwo[2], remainder)
+			}
+		}
+	}
+	return false, s
+}
+
+func partOne() {
+	f, _ := os.Open("input")
+	reader := bufio.NewReader(f)
+	scanner := bufio.NewScanner(reader)
+
+	rules := make([]rule, 134)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if line == "" {
+			break
+		}
+		rule := parseRule(line)
+		rules[rule.name] = rule
+	}
+
+	total := 0
+	for scanner.Scan() {
+		line := scanner.Text()
+		if ok, _ := validateString(rules, 0, line); ok {
+			fmt.Println("VALID:", line)
+			total = total + 1
+		} else {
+			fmt.Println("INVALID:", line)
+		}
+	}
+
+	fmt.Println(total)
+}
+
+func partTwo() {
+	f, _ := os.Open("input")
+	reader := bufio.NewReader(f)
+	scanner := bufio.NewScanner(reader)
+
+	for scanner.Scan() {
+		// line := scanner.Text()
+	}
+}