Day 16

Signed-off-by: Benjamin Hesmans <[email protected]>

d16/d16.go

@@ -0,0 +1,225 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+func panicOnError(e error) {
+	if e != nil {
+		panic(e)
+	}
+}
+
+type ticket struct {
+	vals []int
+}
+
+type minMax struct {
+	min, max int
+}
+
+type rule struct {
+	mm []minMax
+}
+
+type notes struct {
+	myTicket ticket
+	tickets  []ticket
+	rules    map[string]rule
+}
+
+func s2int(s string) int {
+	v, err := strconv.Atoi(s)
+	panicOnError(err)
+	return int(v)
+}
+
+func (r rule) valid(i int) bool {
+	for _, mm := range r.mm {
+		if i >= mm.min && i <= mm.max {
+			return true
+		}
+	}
+
+	return false
+}
+
+func (n notes) valid(i int) bool {
+	for _, r := range n.rules {
+		if r.valid(i) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func (n notes) validTicket(t ticket) (bool, int) {
+	for _, val := range t.vals {
+		if !n.valid(val) {
+			return false, val
+		}
+	}
+	return true, 0
+}
+
+func part1(n notes) int {
+	sum := 0
+	for _, t := range n.tickets {
+		_, v := n.validTicket(t)
+		sum += v
+	}
+	return sum
+}
+
+func newRule(s string) (rule, string) {
+	r := rule{}
+
+	re := regexp.MustCompile(`^([a-z ]*): (.*)$`)
+	t := re.FindStringSubmatch(s)
+	name := t[1]
+
+	s = s[len(name)+2:]
+
+	re = regexp.MustCompile(`^(([0-9]*)-([0-9]*)( or )?)(.*)$`)
+	t = re.FindStringSubmatch(s)
+	for t != nil {
+		r.mm = append(r.mm, minMax{s2int(t[2]), s2int(t[3])})
+		s = s[len(t[1]):]
+		t = re.FindStringSubmatch(s)
+	}
+
+	return r, name
+
+}
+
+func newTicket(s string) ticket {
+	ti := ticket{}
+	ta := strings.Split(s, ",")
+	for _, v := range ta {
+		ti.vals = append(ti.vals, s2int(v))
+	}
+	return ti
+}
+
+func readInput(inputName string) notes {
+	file, err := os.Open(inputName)
+	panicOnError(err)
+	defer file.Close()
+
+	n := notes{rules: make(map[string]rule)}
+
+	scanner := bufio.NewScanner(file)
+	scanner.Scan()
+	l := scanner.Text()
+
+	re := regexp.MustCompile(`^(your ticket:)$`)
+	t := re.FindStringSubmatch(l)
+	for t == nil {
+		if l != "" {
+			r, name := newRule(l)
+			n.rules[name] = r
+		}
+		scanner.Scan()
+		l = scanner.Text()
+		t = re.FindStringSubmatch(l)
+	}
+
+	scanner.Scan()
+	l = scanner.Text()
+	n.myTicket = newTicket(l)
+
+	scanner.Scan()
+	l = scanner.Text()
+	scanner.Scan()
+	l = scanner.Text()
+
+	for scanner.Scan() {
+		l = scanner.Text()
+		n.tickets = append(n.tickets, newTicket(l))
+	}
+
+	err = scanner.Err()
+	panicOnError(err)
+
+	return n
+}
+
+func (n *notes) trimInvalid() {
+	valid := []ticket{}
+	for _, t := range n.tickets {
+		if ok, _ := n.validTicket(t); ok {
+			valid = append(valid, t)
+		}
+	}
+	n.tickets = valid
+}
+
+func (r rule) validForAllTickets(n notes, i int) bool {
+	for _, t := range n.tickets {
+		if !r.valid(t.vals[i]) {
+			return false
+		}
+	}
+	return true
+
+}
+
+func (n *notes) validRuleFor(i int) (bool, string) {
+	ret := ""
+	for k, r := range n.rules {
+		if r.validForAllTickets(*n, i) {
+			if ret != "" {
+				// More that one, give up for this round
+				return false, ""
+			}
+			ret = k
+		}
+	}
+
+	if ret == "" {
+		panic("Haaaaaaaaaaaaaa")
+	}
+
+	delete(n.rules, ret)
+	return true, ret
+}
+
+func part2(n notes) int {
+	n.trimInvalid()
+
+	i2name := make(map[int]string)
+
+	for i := 0; len(i2name) != len(n.myTicket.vals); i = (i + 1) % len(n.myTicket.vals) {
+		if _, ok := i2name[i]; ok {
+			continue
+		}
+
+		if uniq, rs := n.validRuleFor(i); uniq {
+			i2name[i] = rs
+		}
+	}
+
+	mul := 1
+	for k, v := range i2name {
+		if strings.HasPrefix(v, "departure") {
+			mul *= n.myTicket.vals[k]
+		}
+	}
+
+	return mul
+}
+
+func main() {
+	fmt.Println("Hello")
+	// n := readInput("small_input.txt")
+	// n := readInput("small_input2.txt")
+	n := readInput("input.txt")
+	fmt.Printf("%#v\n", part1(n))
+	fmt.Printf("%#v\n", part2(n))
+}