feat: solve part one using direct byte comparaison and efficient hex extraction

internal/2016/DayFive/code.go

@@ -0,0 +1,45 @@
+package dayfive
+
+import (
+	"advent-of-code/internal/registry"
+	"crypto/md5"
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func init() {
+	registry.Register("2016D5", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) string {
+	content, _ := os.ReadFile(filepath)
+	return string(content)
+}
+
+func PartOne(data string) int {
+	doorIDBytes := []byte(data)
+	password := make([]byte, 0, 8)
+	index := 0
+	hexChars := "0123456789abcdef"
+	var buffer []byte
+
+	for len(password) < 8 {
+		buffer = strconv.AppendInt(buffer[:0], int64(index), 10)
+		input := append(doorIDBytes, buffer...)
+		hash := md5.Sum(input)
+
+		if hash[0] == 0 && hash[1] == 0 && hash[2] < 16 {
+			char := hexChars[hash[2]&0x0F]
+			password = append(password, char)
+		}
+		index++
+	}
+
+	fmt.Println(string(password))
+	return 0
+}
+
+func PartTwo(data string) int {
+	return 0
+}