Add solution day 23 part 1 and 2

Author: terminalnode

README.md

@@ -55,7 +55,7 @@ automatically rebuilt and redeployed every time the `common` module or their own
 | 07  | ⭐ ⭐      | 20  | ⭐ ⭐      |
 | 08  | ⭐ ⭐      | 21  |          |
 | 09  | ⭐ ⭐      | 22  | ⭐ ⭐      |
-| 10  | ⭐ ⭐      | 23  |          |
+| 10  | ⭐ ⭐      | 23  | ⭐ ⭐      |
 | 11  | ⭐ ⭐      | 24  |          |
 | 12  | ⭐ ⭐      | 25  |          |
 | 13  | ⭐ ⭐      |     |          |

go.mod

@@ -3,6 +3,7 @@ module github.com/terminalnode/adventofcode2024
 go 1.23.3
 
 require (
+	gonum.org/v1/gonum v0.15.1
 	google.golang.org/grpc v1.68.1
 	google.golang.org/protobuf v1.35.2
 )

go.sum

@@ -2,12 +2,16 @@ github.com/golang/protobuf v1.5.4 h1:i7eJL8qZTpSEXOPTxNKhASYpMn+8e5Q6AdndVa1dWek
 github.com/golang/protobuf v1.5.4/go.mod h1:lnTiLA8Wa4RWRcIUkrtSVa5nRhsEGBg48fD6rSs7xps=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+golang.org/x/exp v0.0.0-20231110203233-9a3e6036ecaa h1:FRnLl4eNAQl8hwxVVC17teOw8kdjVDVAiFMtgUdTSRQ=
+golang.org/x/exp v0.0.0-20231110203233-9a3e6036ecaa/go.mod h1:zk2irFbV9DP96SEBUUAy67IdHUaZuSnrz1n472HUCLE=
 golang.org/x/net v0.29.0 h1:5ORfpBpCs4HzDYoodCDBbwHzdR5UrLBZ3sOnUJmFoHo=
 golang.org/x/net v0.29.0/go.mod h1:gLkgy8jTGERgjzMic6DS9+SP0ajcu6Xu3Orq/SpETg0=
 golang.org/x/sys v0.25.0 h1:r+8e+loiHxRqhXVl6ML1nO3l1+oFoWbnlu2Ehimmi34=
 golang.org/x/sys v0.25.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/text v0.18.0 h1:XvMDiNzPAl0jr17s6W9lcaIhGUfUORdGCNsuLmPG224=
 golang.org/x/text v0.18.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
+gonum.org/v1/gonum v0.15.1 h1:FNy7N6OUZVUaWG9pTiD+jlhdQ3lMP+/LcTpJ6+a8sQ0=
+gonum.org/v1/gonum v0.15.1/go.mod h1:eZTZuRFrzu5pcyjN5wJhcIhnUdNijYxX1T2IcrOGY0o=
 google.golang.org/genproto/googleapis/rpc v0.0.0-20240903143218-8af14fe29dc1 h1:pPJltXNxVzT4pK9yD8vR9X75DaWYYmLGMsEvBfFQZzQ=
 google.golang.org/genproto/googleapis/rpc v0.0.0-20240903143218-8af14fe29dc1/go.mod h1:UqMtugtsSgubUsoxbuAoiCXvqvErP7Gf0so0mK9tHxU=
 google.golang.org/grpc v1.68.1 h1:oI5oTa11+ng8r8XMMN7jAOmWfPZWbYpCFaMUTACxkM0=

solutions/day23/bron-kerbosch.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"gonum.org/v1/gonum/graph/simple"
+)
+
+// I believe something like this is implemented in gonum already, seems
+// like it anyway, but I've already cheated on the graph DS so might at
+// least implement the algorithm myself.
+
+func bronKerbosch(
+	r []int64,
+	p []int64,
+	g *simple.UndirectedGraph,
+) [][]int64 {
+	// If P is empty, this is a maximal click
+	if len(p) == 0 {
+		return [][]int64{r}
+	}
+	out := make([][]int64, 0, len(p))
+	x := make(map[int64]bool)
+
+	existInP := make(map[int64]bool)
+	for _, pEntry := range p {
+		existInP[pEntry] = true
+	}
+
+	for _, v := range p {
+		skipV := false
+
+		fromV := g.From(v)
+		newP := make([]int64, 0, fromV.Len())
+		for fromV.Next() {
+			id := fromV.Node().ID()
+			if !existInP[id] {
+				continue
+			}
+
+			if x[id] {
+				// X set would not be empty, and thus can't return anything
+				skipV = true
+				break
+			}
+			newP = append(newP, id)
+		}
+
+		if !skipV {
+			newR := append([]int64{v}, r...)
+			out = append(out, bronKerbosch(newR, newP, g)...)
+		}
+		x[v] = true
+	}
+
+	return out
+}

solutions/day23/main.go

@@ -1,9 +1,71 @@
 package main
 
 import (
+	"fmt"
 	"github.com/terminalnode/adventofcode2024/common"
+	"slices"
+	"strings"
 )
 
 func main() {
-	common.Setup(23, nil, nil)
+	common.Setup(23, part1, part2)
+}
+
+func part1(
+	input string,
+) string {
+	cm, err := parse(input)
+	if err != nil {
+		return fmt.Sprintf("Failed to parse input: %v", err)
+	}
+
+	visited := make(map[string]bool)
+	for name1, conn1 := range cm {
+		for name2, conn2 := range conn1.connMap {
+			for name3, conn3 := range conn2.connMap {
+				if conn3.connMap[name1] != nil {
+					if name1[0] == 't' || name2[0] == 't' || name3[0] == 't' {
+						names := []string{name1, name2, name3}
+						slices.Sort(names)
+						visited[strings.Join(names, "-")] = true
+					}
+				}
+			}
+		}
+	}
+
+	return fmt.Sprintf("Clusters of 3 with computers starting with t: %d", len(visited))
+}
+
+func part2(
+	input string,
+) string {
+	graph, intToName, err := parseGonumGraph(input)
+	if err != nil {
+		return fmt.Sprintf("Failed to parse input: %v", err)
+	}
+
+	nodes := graph.Nodes()
+	p := make([]int64, 0, nodes.Len())
+	for nodes.Next() {
+		p = append(p, nodes.Node().ID())
+	}
+
+	cliques := bronKerbosch([]int64{}, p, graph)
+
+	var biggest []int64
+	for _, c := range cliques {
+		if len(c) > len(biggest) {
+			biggest = c
+		}
+	}
+
+	names := make([]string, len(biggest))
+	for i, n := range biggest {
+		names[i] = intToName[n]
+	}
+	slices.Sort(names)
+	name := strings.Join(names, ",")
+
+	return fmt.Sprintf("Password: %s", name)
 }

solutions/day23/parse.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"fmt"
+	"gonum.org/v1/gonum/graph"
+	"gonum.org/v1/gonum/graph/simple"
+	"strings"
+)
+
+type connection struct {
+	name    nodeName
+	connMap connMap
+}
+type nodeName = string
+type connMap map[nodeName]*connection
+
+type textNode struct {
+	id   int64
+	name string
+}
+
+func (n textNode) ID() int64 {
+	return n.id
+}
+
+func parseGonumGraph(
+	input string,
+) (*simple.UndirectedGraph, map[int64]string, error) {
+	out := simple.NewUndirectedGraph()
+	visited := make(map[string]graph.Node)
+	intToName := make(map[int64]string)
+
+	idCounter := int64(0)
+
+	lines := strings.Split(input, "\n")
+	for _, line := range lines {
+		split := strings.Split(line, "-")
+		if len(split) != 2 {
+			return out, intToName, fmt.Errorf("length after splitting '%s' should be 2, was %d", line, len(split))
+		}
+		name1 := split[0]
+		name2 := split[1]
+
+		if visited[name1] == nil {
+			idCounter++
+			visited[name1] = simple.Node(idCounter)
+			intToName[idCounter] = name1
+			out.AddNode(visited[name1])
+		}
+		if visited[name2] == nil {
+			idCounter++
+			visited[name2] = simple.Node(idCounter)
+			intToName[idCounter] = name2
+			out.AddNode(visited[name2])
+		}
+		out.SetEdge(simple.Edge{F: visited[name1], T: visited[name2]})
+	}
+
+	return out, intToName, nil
+}
+
+func parse(
+	input string,
+) (connMap, error) {
+	lines := strings.Split(input, "\n")
+	out := make(connMap)
+
+	for _, line := range lines {
+		split := strings.Split(line, "-")
+		if len(split) != 2 {
+			return out, fmt.Errorf("length after splitting '%s' should be 2, was %d", line, len(split))
+		}
+		out.addConnection(split[0], split[1])
+	}
+
+	return out, nil
+}
+
+func (m connMap) addConnection(
+	n1 nodeName,
+	n2 nodeName,
+) {
+	node1 := m.getOrCreateNode(n1)
+	node2 := m.getOrCreateNode(n2)
+	node1.connMap[n2] = node2
+	node2.connMap[n1] = node1
+}
+
+func (m connMap) getOrCreateNode(
+	name nodeName,
+) *connection {
+	if n, ok := m[name]; ok {
+		return n
+	}
+	m[name] = &connection{name: name, connMap: make(connMap)}
+	return m[name]
+}