Day 4: Part 1 and 2

four/day_four.go

@@ -0,0 +1,224 @@
+package four
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+type passport struct {
+	byr, iyr, eyr, hgt, hcl, ecl, pid, cid string
+}
+
+func (p *passport) validate(strict bool, optional ...string) bool {
+	valid := true
+	requiredFields := []string{"byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid", "cid"}
+	filtered := []string{}
+	// remove optional fields
+	for _, f := range requiredFields {
+		required := true
+		for _, o := range optional {
+			if f == o {
+				required = false
+				break
+			}
+		}
+		if required {
+			filtered = append(filtered, f)
+		}
+	}
+
+	for _, f := range filtered {
+		if strict {
+			if !p.validateField(f) {
+				valid = false
+			}
+		} else {
+			if p.getField(f) == "" {
+				valid = false
+			}
+		}
+	}
+
+	return valid
+}
+
+func (p *passport) validateField(code string) bool {
+	switch code {
+	case "byr":
+		year, err := strconv.Atoi(p.byr)
+		if err != nil {
+			return false
+		}
+		return year >= 1920 && year <= 2002
+	case "iyr":
+		year, err := strconv.Atoi(p.iyr)
+		if err != nil {
+			return false
+		}
+		return year >= 2010 && year <= 2020
+	case "eyr":
+		year, err := strconv.Atoi(p.eyr)
+		if err != nil {
+			return false
+		}
+		return year >= 2020 && year <= 2030
+	case "hgt":
+		var height int
+		var unit string
+		count, err := fmt.Sscanf(p.hgt, "%d%s", &height, &unit)
+		if count != 2 || err != nil {
+			return false
+		}
+		if unit == "in" {
+			return height >= 59 && height <= 76
+		}
+		return height >= 150 && height <= 193
+	case "hcl":
+		if len(p.hcl) != 7 {
+			return false
+		}
+		var validColour = regexp.MustCompile(`^#[a-z0-9]+$`)
+		return validColour.MatchString(p.hcl)
+	case "ecl":
+		switch p.ecl {
+		case "amb", "blu", "brn", "gry", "grn", "hzl", "oth":
+			return true
+		default:
+			return false
+		}
+	case "pid":
+		if len(p.pid) != 9 {
+			return false
+		}
+		var validColour = regexp.MustCompile(`^[0-9]+$`)
+		return validColour.MatchString(p.pid)
+	default:
+		return false
+	}
+}
+
+func (p *passport) getField(code string) string {
+	switch code {
+	case "byr":
+		return p.byr
+	case "iyr":
+		return p.iyr
+	case "eyr":
+		return p.eyr
+	case "hgt":
+		return p.hgt
+	case "hcl":
+		return p.hcl
+	case "ecl":
+		return p.ecl
+	case "pid":
+		return p.pid
+	case "cid":
+		return p.cid
+	default:
+		return ""
+	}
+}
+
+func (p *passport) setField(code, value string) {
+	switch code {
+	case "byr":
+		p.byr = value
+	case "iyr":
+		p.iyr = value
+	case "eyr":
+		p.eyr = value
+	case "hgt":
+		p.hgt = value
+	case "hcl":
+		p.hcl = value
+	case "ecl":
+		p.ecl = value
+	case "pid":
+		p.pid = value
+	case "cid":
+		p.cid = value
+	default:
+		return
+	}
+}
+
+type customs struct {
+	passports []passport
+}
+
+func (c *customs) load(filename string) error {
+	file, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	var p *passport
+	for scanner.Scan() {
+		if scanner.Text() == "" {
+			// Blank line means we have moved on to the next passport
+			if p != nil {
+				c.passports = append(c.passports, *p)
+				p = nil
+			}
+			continue
+		}
+
+		if p == nil {
+			p = &passport{}
+		}
+
+		fields := strings.Split(scanner.Text(), " ")
+		for _, f := range fields {
+			var key, value string
+			count, err := fmt.Sscanf(f, "%3s:%s", &key, &value)
+			if count != 2 || err != nil {
+				return fmt.Errorf("Unable to parse field %s: %w", f, err)
+			}
+
+			p.setField(key, value)
+		}
+	}
+	// commit the last passport if there isn't a blank line
+	if p != nil {
+		c.passports = append(c.passports, *p)
+	}
+
+	return nil
+}
+
+func (c *customs) check(strict bool, optional ...string) int {
+	valid := 0
+
+	for _, p := range c.passports {
+		if p.validate(strict, optional...) {
+			valid++
+		}
+	}
+
+	return valid
+}
+
+// PartOne find all the valid passports
+func PartOne() string {
+	customs := customs{}
+	customs.load("four/passports.txt")
+	validPassports := customs.check(false, "cid")
+
+	return fmt.Sprintf("Found %d valid passports", validPassports)
+}
+
+// PartTwo Strictly find all the valid passports
+func PartTwo() string {
+	customs := customs{}
+	customs.load("four/passports.txt")
+	validPassports := customs.check(true, "cid")
+
+	return fmt.Sprintf("Found %d strictly valid passports", validPassports)
+}