Solve Day 2

Signed-off-by: Alexander Kurbatov <sir.alkurbatov@yandex.ru>

Author: alkurbatov

2023/2/main.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"log"
+	"os"
+	"regexp"
+	"strconv"
+)
+
+const (
+	maxRed   = 12
+	maxGreen = 13
+	maxBlue  = 14
+)
+
+var ErrNoID = errors.New("game ID not found")
+
+var (
+	gameID = regexp.MustCompile(`Game (\d+):`)
+	blues  = regexp.MustCompile(` (\d+) blue`)
+	reds   = regexp.MustCompile(` (\d+) red`)
+	greens = regexp.MustCompile(` (\d+) green`)
+)
+
+func extractGameID(src string) (int, error) {
+	raw := gameID.FindStringSubmatch(src)
+	if len(raw) == 0 {
+		return 0, ErrNoID
+	}
+
+	return strconv.Atoi(raw[1])
+}
+
+func fewestPossible(src string, re *regexp.Regexp) int {
+	counts := re.FindAllStringSubmatch(src, -1)
+	if counts == nil {
+		return 0
+	}
+
+	localMax := -1
+
+	for _, count := range counts {
+		for i := 1; i < len(count); i++ {
+			num, err := strconv.Atoi(count[i])
+			if err != nil {
+				log.Printf("Failed to extract balls count: %v", err)
+				return -1
+			}
+
+			if num > localMax {
+				localMax = num
+			}
+		}
+	}
+
+	return localMax
+}
+
+func main() {
+	input, err := os.Open("./2023/2/input.txt")
+	if err != nil {
+		log.Printf("Failed to open input.txt: %v", err)
+		return
+	}
+	defer input.Close()
+
+	var firstPartResult, secondPartResult int
+
+	scanner := bufio.NewScanner(input)
+	for scanner.Scan() {
+		src := scanner.Text()
+
+		fewerRed := fewestPossible(src, reds)
+		fewerBlue := fewestPossible(src, blues)
+		fewerGreen := fewestPossible(src, greens)
+
+		secondPartResult += fewerRed * fewerBlue * fewerGreen
+
+		if fewerRed > maxRed || fewerBlue > maxBlue || fewerGreen > maxGreen {
+			continue
+		}
+
+		id, err := extractGameID(src)
+		if err != nil {
+			log.Printf("Failed to extract game ID: %v", err)
+			return
+		}
+
+		firstPartResult += id
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Printf("Failed to scan input.txt: %v", err)
+		return
+	}
+
+	log.Printf("Part 1 result: %d", firstPartResult)
+	log.Printf("Part 2 result: %d", secondPartResult)
+}