add day 23 with questionable solution

23/alt/main.go

@@ -0,0 +1,130 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"maps"
+	"os"
+	"sort"
+	"strings"
+	"time"
+)
+
+func catch(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+func main() {
+	flag.Parse()
+	if flag.NArg() != 1 {
+		fmt.Println("Usage: go run . input.txt")
+		os.Exit(1)
+	}
+
+	bs, err := os.ReadFile(flag.Arg(0))
+	catch(err)
+
+	parsed := parseInput(string(bs))
+	part1(parsed)
+	part2(parsed)
+}
+
+type Parsed map[string]map[string]bool
+
+func parseInput(input string) Parsed {
+	lines := strings.Split(input, "\n")
+	if len(lines[len(lines)-1]) == 0 {
+		lines = lines[:len(lines)-1]
+	}
+	parsed := make(Parsed)
+	for _, line := range lines {
+		parts := strings.Split(line, "-")
+		if parsed[parts[0]] == nil {
+			parsed[parts[0]] = make(map[string]bool)
+		}
+		if parsed[parts[1]] == nil {
+			parsed[parts[1]] = make(map[string]bool)
+		}
+		parsed[parts[0]][parts[1]] = true
+		parsed[parts[1]][parts[0]] = true
+	}
+	return parsed
+}
+
+type Triplet [3]string
+
+func part1(parsed Parsed) {
+	timeStart := time.Now()
+	// find triplets, where each computes is connected to the other two
+
+	triplets := make(map[Triplet]bool)
+	for c1, cs := range parsed {
+		for c2 := range cs {
+			for c3 := range parsed[c2] {
+				if c3 == c1 {
+					continue
+				}
+				if !parsed[c3][c1] {
+					continue
+				}
+				t := Triplet{c1, c2, c3}
+
+				if c1[0] == 't' || c2[0] == 't' || c3[0] == 't' {
+					sort.Strings(t[:])
+					triplets[t] = true
+				}
+			}
+		}
+	}
+
+	fmt.Printf("Part 1: %d\t\tin %v\n", len(triplets), time.Since(timeStart))
+}
+
+type Party map[string]bool
+
+var calls int
+
+func dfs(connected Parsed, visited Party) Party {
+	calls++
+	var largestParty Party
+NextC:
+	for c := range connected {
+		if visited[c] {
+			continue
+		}
+		// check if c is connected to all visited
+		for prev := range visited {
+			if !connected[c][prev] {
+				continue NextC
+			}
+		}
+		// it is connected to all visited, so we can add it to the party
+
+		visited[c] = true
+		party := dfs(connected, visited)
+		if len(party) > len(largestParty) {
+			largestParty = party
+		}
+		delete(visited, c)
+	}
+	if len(largestParty) == 0 {
+		largestParty = maps.Clone(visited)
+	}
+	return largestParty
+}
+
+// does it need memo? :)
+func part2(parsed Parsed) {
+	timeStart := time.Now()
+
+	largestParty := dfs(parsed, make(Party))
+	fmt.Printf("calls: %d\n", calls)
+	sorted := make([]string, 0, len(largestParty))
+	for c := range largestParty {
+		sorted = append(sorted, c)
+	}
+	sort.Strings(sorted)
+	fmt.Printf("Part 2: %d, %v\t\tin %v\n", len(largestParty), strings.Join(sorted, ","), time.Since(timeStart))
+}