feat: extract shared functions and solve part two

internal/2022/DayThree/code.go

@@ -10,6 +10,43 @@ func init() {
 	registry.Register("2022D3", ParseInput, PartOne, PartTwo)
 }
 
+func buildItemSet(items string) map[rune]bool {
+	itemSet := make(map[rune]bool)
+	for _, item := range items {
+		itemSet[item] = true
+	}
+	return itemSet
+}
+
+func findCommonItem(itemSet map[rune]bool, items string) rune {
+	for _, item := range items {
+		if itemSet[item] {
+			return item
+		}
+	}
+	return 0
+}
+
+func findIntersection(itemSet map[rune]bool, items string) map[rune]bool {
+	intersection := make(map[rune]bool)
+	for _, item := range items {
+		if itemSet[item] {
+			intersection[item] = true
+		}
+	}
+	return intersection
+}
+
+func getItemPriority(item rune) int {
+	if item >= 'a' && item <= 'z' {
+		return int(item - 'a' + 1)
+	}
+	if item >= 'A' && item <= 'Z' {
+		return int(item - 'A' + 27)
+	}
+	return 0
+}
+
 func ParseInput(filepath string) []string {
 	content, _ := os.ReadFile(filepath)
 	return strings.Split(string(content), "\n")
@@ -22,29 +59,29 @@ func PartOne(data []string) int {
 		firstCompartment := rucksack[:compartmentSize]
 		secondCompartment := rucksack[compartmentSize:]
 
-		firstCompartmentItems := make(map[rune]bool)
-		for _, item := range firstCompartment {
-			firstCompartmentItems[item] = true
-		}
-
-		var commonItem rune
-		for _, item := range secondCompartment {
-			if firstCompartmentItems[item] {
-				commonItem = item
-				break
-			}
-		}
-
-		if commonItem >= 'a' && commonItem <= 'z' {
-			totalPriority += int(commonItem - 'a' + 1)
-		} else if commonItem >= 'A' && commonItem <= 'Z' {
-			totalPriority += int(commonItem - 'A' + 27)
-		}
+		firstCompartmentItems := buildItemSet(firstCompartment)
+		commonItem := findCommonItem(firstCompartmentItems, secondCompartment)
+		totalPriority += getItemPriority(commonItem)
 	}
 
 	return totalPriority
 }
 
 func PartTwo(data []string) int {
-	return 0
+	totalPriority := 0
+	for i := 0; i < len(data); i += 3 {
+		if i+2 >= len(data) {
+			break
+		}
+		firstRucksack := data[i]
+		secondRucksack := data[i+1]
+		thirdRucksack := data[i+2]
+
+		firstRucksackItems := buildItemSet(firstRucksack)
+		commonInFirstTwo := findIntersection(firstRucksackItems, secondRucksack)
+		badge := findCommonItem(commonInFirstTwo, thirdRucksack)
+		totalPriority += getItemPriority(badge)
+	}
+
+	return totalPriority
 }