aoc2024/day-23/internal/one/solve.go

package one

import (
	"bytes"
	"slices"
	"strings"

	"github.com/onyx-and-iris/aoc2024/day-23/internal/set"
)

func Solve(buf []byte) (int, error) {
	r := bytes.NewReader(buf)
	connections, err := parseLines(r)
	if err != nil {
		return 0, err
	}

	networks := make(map[string]*set.Set)
	for _, connection := range connections {
		if _, found := networks[connection[0]]; !found {
			networks[connection[0]] = set.New()
		}
		networks[connection[0]].Add(connection[1])

		if _, found := networks[connection[1]]; !found {
			networks[connection[1]] = set.New()
		}
		networks[connection[1]].Add(connection[0])
	}

	setIdentifiers := make(map[string]struct{})
	for name := range networks {
		if !strings.HasPrefix(name, "t") {
			continue
		}

		for _, node := range networks[name].List() {
			for _, node2 := range networks[node].List() {
				if slices.Contains(networks[node2].List(), name) {
					s := set.New()
					s.Add(name)
					s.Add(node)
					s.Add(node2)
					setIdentifiers[s.String()] = struct{}{}
				}
			}
		}
	}

	return len(setIdentifiers), nil
}