feat: use a BFS approach to solve part one

internal/2020/DaySeven/code.go

@@ -0,0 +1,70 @@
+package dayseven
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"regexp"
+	"strings"
+)
+
+func init() {
+	registry.Register("2020D7", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	reverseGraph := make(map[string][]string)
+	rulePattern := regexp.MustCompile(`^(\w+ \w+) bags contain (.+)\.$`)
+	containedPattern := regexp.MustCompile(`(\d+) (\w+ \w+) bags?`)
+
+	for _, line := range data {
+		matches := rulePattern.FindStringSubmatch(line)
+		if len(matches) != 3 {
+			continue
+		}
+
+		containerBag := matches[1]
+		containedString := matches[2]
+
+		if containedString == "no other bags" {
+			continue
+		}
+
+		containedMatches := containedPattern.FindAllStringSubmatch(containedString, -1)
+		for _, match := range containedMatches {
+			if len(match) >= 3 {
+				containedBag := match[2]
+				reverseGraph[containedBag] = append(reverseGraph[containedBag], containerBag)
+			}
+		}
+	}
+
+	visited := make(map[string]bool)
+	queue := reverseGraph["shiny gold"]
+
+	for len(queue) > 0 {
+		current := queue[0]
+		queue = queue[1:]
+
+		if visited[current] {
+			continue
+		}
+		visited[current] = true
+
+		for _, parent := range reverseGraph[current] {
+			if !visited[parent] {
+				queue = append(queue, parent)
+			}
+		}
+	}
+
+	return len(visited)
+}
+
+func PartTwo(data []string) int {
+	return 0
+}