(Bonus) alternative solution for the first part of AoC2020 day 7

AoC2020-day07_1-graph.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

type Rule struct {
	content string
	quantity int
}

type RuleGraph struct {
	nodes []*Rule
	edges map[Rule][]*Rule
}

func (g *RuleGraph) AddNode(n *Rule) {
	g.nodes = append(g.nodes, n)
}

func (g *RuleGraph) AddEdge(n1, n2 *Rule) {
	if g.edges == nil {
		g.edges = make(map[Rule][]*Rule)
	}
	g.edges[*n1] = append(g.edges[*n1], n2)
	g.edges[*n2] = append(g.edges[*n2], n1)
}

func sanitizeRule(rule string) string {
	res := strings.ReplaceAll(rule, " bags", "")
	res = strings.ReplaceAll(res, " bag", "")
	res = strings.ReplaceAll(res, ".", "")
	res = strings.TrimSpace(res)
	return res
}

func parseRule(rule string, tree *RuleGraph) {
	header := sanitizeRule(strings.Split(rule, "contain")[0])
	content := sanitizeRule(strings.Split(rule, "contain")[1])

	var node = Rule{header, -1}
	tree.AddNode(&node)
	for _, c := range strings.Split(content, ",") {
		c = sanitizeRule(c)
		quantity, _ := strconv.Atoi(string(c[0]))
		c = c[2:]
		node2 := Rule{c, quantity}
		tree.AddNode(&node2)
		tree.AddEdge(&node, &node2)
	}
}

func alreadyInArray(x *[]string, element string) bool {
	for _, c := range *x {
		if element == c {
			return true
		}
	}
	return false
}

func navigateTree(g *RuleGraph, query string, seen *[]string) int {
	count := 1
	for i := 0; i < len(g.nodes); i++ {
		near := g.edges[*g.nodes[i]]
		for j := 0; j < len(near); j++ {
			if near[j].quantity == -1 {
				continue
			}
			if near[j].content == query {
				if alreadyInArray(seen, g.nodes[i].content) {
					continue
				}
				count = count + navigateTree(g, g.nodes[i].content, seen)
				*seen = append(*seen, g.nodes[i].content)
			}
		}
	}
	return count
}

func main() {
	f, _ := os.Open("input.txt")
	b := bufio.NewScanner(f)
	var root RuleGraph
	i := 0
	for b.Scan() {
		line := b.Text()
		parseRule(line, &root)
		i++
	}
	seen := make([]string, 0, i)
	part1 := navigateTree(&root, "shiny gold", &seen)-1
	fmt.Println("Answer (part 1):", part1)
}