adventofcode/2024/day23/main.go

package main

import (
	"fmt"
	"sort"
	"strings"

	h "git.bullercodeworks.com/brian/adventofcode/helpers"
)

func main() {
	inp := h.StdinToStringSlice()
	part1(inp)
	fmt.Println()
	part2(inp)
}

func parseInput(inp []string) NetworkMap {
	network := make(map[string]h.Set)
	for _, l := range inp {
		pts := strings.Split(l, "-")
		if _, ok := network[pts[0]]; !ok {
			network[pts[0]] = h.NewSet(1)
		}
		if _, ok := network[pts[1]]; !ok {
			network[pts[1]] = h.NewSet(1)
		}
		network[pts[0]].Add(pts[1])
		network[pts[1]].Add(pts[0])
	}
	return NewNetworkMap(network)
}

func part1(inp []string) {
	nwk := parseInput(inp)
	fmt.Println("# Part 1")
	total := 0
	wrk := nwk
	for _, comp := range wrk.Comps {
		conns := make([]string, 0, len(comp.Conns))
		for name := range comp.Conns {
			conns = append(conns, name)
			total++
		}
	}
	tris := wrk.FindTGroups()
	fmt.Println(len(tris))
}

func part2(inp []string) {
	nwk := parseInput(inp)
	cnt := len(nwk.Comps)
	wrk := h.NewSet(cnt)
	for nm := range nwk.Comps {
		wrk.Add(nm)
	}
	group := BronKerbosch(h.NewSet(cnt+1), wrk, h.NewSet(cnt+1), h.NewSet(0), nwk.Network)
	fmt.Println("Group Size:", group.Size())
	fmt.Println("Password:", strings.Join(group.ToSortedSlice(), ","))
}

func BronKerbosch(cl, chk, excl, kmax h.Set, graph map[string]h.Set) h.Set {
	if chk.Empty() && excl.Empty() {
		return cl
	}
	for vx := range chk {
		vxSet := h.NewSetFromValues(vx)
		vxConns := graph[vx]
		nC := cl.Union(vxSet)
		nWrk := chk.Intersection(vxConns)
		if nC.Size()+nWrk.Size() <= kmax.Size() {
			continue
		}
		newExcl := excl.Intersection(vxConns)
		fC := BronKerbosch(nC, nWrk, newExcl, kmax, graph)
		if fC.Size() > kmax.Size() {
			kmax = fC
		}
		chk.Remove(vx)
		excl.Add(vx)
	}
	return kmax
}

type NetworkMap struct {
	Network map[string]h.Set
	Comps   map[string]*Comp
}

func NewNetworkMap(nwk map[string]h.Set) NetworkMap {
	nm := NetworkMap{Network: nwk, Comps: make(map[string]*Comp)}
	for name, conns := range nwk {
		for conn := range conns {
			nm.Connect(name, conn)
		}
	}
	return nm
}

func (n *NetworkMap) Connect(c1, c2 string) {
	n.GetComputer(c1).Connect(n.GetComputer(c2))
}

func (n *NetworkMap) GetComputer(nm string) *Comp {
	if cm, ok := n.Comps[nm]; ok {
		return cm
	}
	cm := NewComp(nm)
	n.Comps[nm] = cm
	return cm
}

func (n *NetworkMap) FindTGroups() map[Group]bool {
	ret := make(map[Group]bool)
	chk := make(map[string]bool)
	for cn, comp := range n.Comps {
		if chk[cn] {
			continue
		}
		for nn, next := range comp.Conns {
			friends := comp.FindFriends(next)
			for _, friend := range friends {
				if cn[0] == 't' || nn[0] == 't' || friend[0] == 't' {
					grp := NewGroup([3]string{cn, nn, friend})
					ret[grp] = true
				}
			}
			chk[cn] = true
		}
	}
	return ret
}

type Group struct {
	Comps [3]string
}

func NewGroup(nodes [3]string) Group {
	s := nodes[:]
	sort.Strings(s)
	return Group{Comps: [3]string{s[0], s[1], s[2]}}
}

func (g Group) String() string {
	return fmt.Sprintf("%s-%s-%s", g.Comps[0], g.Comps[1], g.Comps[2])
}

type Comp struct {
	Name  string
	Conns map[string]*Comp
}

func NewComp(n string) *Comp {
	return &Comp{Name: n, Conns: make(map[string]*Comp)}
}

func (c *Comp) Connect(o *Comp) {
	c.Conns[o.Name] = o
	o.Conns[c.Name] = c
}

func (c *Comp) FindFriends(o *Comp) []string {
	var friends []string
	checked := make(map[string]bool)
	for name := range c.Conns {
		if name == c.Name || name == o.Name {
			continue
		}
		if _, ok := checked[name]; ok {
			continue
		}
		if _, ok := o.Conns[name]; !ok {
			continue
		}
		friends = append(friends, name)
		checked[name] = true
	}
	return friends
}