Day 16: Ticket Translation (Part 1 only)

Author: frux

day16/day16.go

@@ -0,0 +1,101 @@
+package day16
+
+import (
+	"adventofcode-2020/input"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+const INPUT = "./day16/input.txt"
+
+func Part1() string {
+	entries := input.ReadStrings(INPUT)
+	fields := []*Field{}
+
+	for _, entry := range entries {
+		if entry == "" {
+			break
+		}
+
+		fields = append(fields, parseField(entry))
+	}
+
+	myTicketIndex := len(fields) + 2
+	nearbyTicketsIndex := myTicketIndex + 3
+	errorRate := 0
+
+	for i := nearbyTicketsIndex; i < len(entries); i++ {
+		ticket := parseTicket(entries[i])
+
+		for _, value := range ticket {
+			if !isValidForAnyField(fields, value) {
+				errorRate += value
+			}
+		}
+	}
+
+	return fmt.Sprint(errorRate)
+}
+
+func Part2() string {
+	return "skipped"
+}
+
+func isValidForAnyField(fields []*Field, value int) bool {
+	for _, field := range fields {
+		if isValidForField(field, value) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func isValidForField(field *Field, value int) bool {
+	for _, limits := range field.Ranges {
+		if value >= limits[0] && value <= limits[1] {
+			return true
+		}
+	}
+
+	return false
+}
+
+func parseTicket(line string) []int {
+	parts := strings.Split(line, ",")
+	ticket := make([]int, len(parts))
+
+	for i, part := range parts {
+		value, _ := strconv.Atoi(part)
+		ticket[i] = value
+	}
+
+	return ticket
+}
+
+func parseField(line string) *Field {
+	parts := strings.Split(line, ": ")
+	return &Field{
+		Name:   parts[0],
+		Ranges: parseRanges(parts[1]),
+	}
+}
+
+func parseRanges(line string) [][2]int {
+	parts := strings.Split(line, " or ")
+	ranges := make([][2]int, len(parts))
+	for i, part := range parts {
+		numbers := strings.Split(part, "-")
+		min, _ := strconv.Atoi(numbers[0])
+		max, _ := strconv.Atoi(numbers[1])
+		ranges[i] = [2]int{min, max}
+	}
+
+	return ranges
+}
+
+type Field struct {
+	Name   string
+	Ranges [][2]int
+}