From 43b78620ca36245b66c61db6b7e8e17319d1ea2f Mon Sep 17 00:00:00 2001
From: Kharec <sandro@cazzaniga.fr>
Date: Mon, 24 Nov 2025 18:49:12 +0100
Subject: [PATCH] feat: add main code

---
 2020/day04/main.go | 159 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 159 insertions(+)
 create mode 100644 2020/day04/main.go

diff --git a/2020/day04/main.go b/2020/day04/main.go
new file mode 100644
index 0000000..db47628
--- /dev/null
+++ b/2020/day04/main.go
@@ -0,0 +1,159 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func parseInput(file string) []string {
+	content, err := os.ReadFile(file)
+	if err != nil {
+		log.Fatalf("Failed to read input file: %v", err)
+	}
+
+	text := string(content)
+	passports := strings.Split(text, "\n\n")
+
+	result := make([]string, 0, len(passports))
+	for _, passport := range passports {
+		passport = strings.TrimSpace(passport)
+		if passport == "" {
+			continue
+		}
+		passport = strings.ReplaceAll(passport, "\n", " ")
+		passport = strings.Join(strings.Fields(passport), " ")
+		result = append(result, passport)
+	}
+	return result
+}
+
+func PartOne(data []string) int {
+	count := 0
+	required := []string{"byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid"}
+	for _, passport := range data {
+		fields := strings.Fields(passport)
+		present := make(map[string]bool)
+		for _, field := range fields {
+			if idx := strings.Index(field, ":"); idx != -1 {
+				present[field[:idx]] = true
+			}
+		}
+		missing := false
+		for _, field := range required {
+			if !present[field] {
+				missing = true
+				break
+			}
+		}
+		if !missing {
+			count++
+		}
+	}
+	return count
+}
+
+func PartTwo(data []string) int {
+	isNumberInRange := func(value string, min, max int, digits int) bool {
+		if len(value) != digits {
+			return false
+		}
+		n, err := strconv.Atoi(value)
+		if err != nil {
+			return false
+		}
+		return n >= min && n <= max
+	}
+
+	isValidHeight := func(value string) bool {
+		if len(value) < 3 {
+			return false
+		}
+		unit := value[len(value)-2:]
+		number := value[:len(value)-2]
+		n, err := strconv.Atoi(number)
+		if err != nil {
+			return false
+		}
+		if unit == "cm" {
+			return n >= 150 && n <= 193
+		}
+		if unit == "in" {
+			return n >= 59 && n <= 76
+		}
+		return false
+	}
+
+	isValidHairColor := func(value string) bool {
+		if len(value) != 7 || value[0] != '#' {
+			return false
+		}
+		for _, c := range value[1:] {
+			if !((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f')) {
+				return false
+			}
+		}
+		return true
+	}
+
+	isValidPID := func(value string) bool {
+		if len(value) != 9 {
+			return false
+		}
+		for _, c := range value {
+			if c < '0' || c > '9' {
+				return false
+			}
+		}
+		return true
+	}
+
+	validECL := map[string]bool{
+		"amb": true, "blu": true, "brn": true, "gry": true,
+		"grn": true, "hzl": true, "oth": true,
+	}
+
+	required := []string{"byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid"}
+	count := 0
+
+	for _, passport := range data {
+		fields := map[string]string{}
+		for field := range strings.FieldsSeq(passport) {
+			parts := strings.SplitN(field, ":", 2)
+			if len(parts) == 2 {
+				fields[parts[0]] = parts[1]
+			}
+		}
+
+		passportValidators := map[string]func(string) bool{
+			"byr": func(v string) bool { return isNumberInRange(v, 1920, 2002, 4) },
+			"iyr": func(v string) bool { return isNumberInRange(v, 2010, 2020, 4) },
+			"eyr": func(v string) bool { return isNumberInRange(v, 2020, 2030, 4) },
+			"hgt": isValidHeight,
+			"hcl": isValidHairColor,
+			"ecl": func(v string) bool { return validECL[v] },
+			"pid": isValidPID,
+		}
+
+		valid := true
+		for _, key := range required {
+			value, ok := fields[key]
+			if !ok || !passportValidators[key](value) {
+				valid = false
+				break
+			}
+		}
+		if valid {
+			count++
+		}
+	}
+	return count
+}
+
+func main() {
+	data := parseInput("input.txt")
+	fmt.Println("Part 1:", PartOne(data))
+	fmt.Println("Part 2:", PartTwo(data))
+}