feat: completed day 11 for advent of code

2025/cmd/root.go

@@ -19,6 +19,7 @@ import (
 	"cpatino.com/advent-of-code/2025/day08"
 	"cpatino.com/advent-of-code/2025/day09"
 	"cpatino.com/advent-of-code/2025/day10"
+	"cpatino.com/advent-of-code/2025/day11"
 )
 
 var days = map[int]func(string) (any, any){
@@ -32,6 +33,7 @@ var days = map[int]func(string) (any, any){
 	8:  day08.Run,
 	9:  day09.Run,
 	10: day10.Run,
+	11: day11.Run,
 }
 
 var rootCmd = &cobra.Command{

2025/day11/day11.go

@@ -0,0 +1,119 @@
+package day11
+
+import (
+	"bufio"
+	"os"
+	"strings"
+)
+
+type Key struct {
+	node string
+	mask uint8
+}
+
+func countPaths(graph map[string][]string, start, target string) int {
+	memo := make(map[string]int)
+	visiting := make(map[string]bool)
+	var dfs func(string) int
+	dfs = func(u string) int {
+		if u == target {
+			return 1
+		}
+		if visiting[u] {
+			return 0
+		}
+		if v, ok := memo[u]; ok {
+			return v
+		}
+		visiting[u] = true
+		total := 0
+		for _, v := range graph[u] {
+			total += dfs(v)
+		}
+		visiting[u] = false
+		memo[u] = total
+		return total
+	}
+	return dfs(start)
+}
+
+func Part1(graph map[string][]string) int {
+	return countPaths(graph, "you", "out")
+}
+
+func Part2(graph map[string][]string) int {
+	start, target := "svr", "out"
+	const need1, need2 = "dac", "fft"
+
+	memo := make(map[Key]int)
+	visiting := make(map[string]bool)
+	var dfs func(string, uint8) int
+	dfs = func(u string, mask uint8) int {
+		if u == need1 {
+			mask |= 0b01
+		}
+		if u == need2 {
+			mask |= 0b10
+		}
+
+		if u == target {
+			if mask == 0b11 {
+				return 1
+			}
+			return 0
+		}
+
+		if visiting[u] {
+			return 0
+		}
+
+		k := Key{u, mask}
+		if v, ok := memo[k]; ok {
+			return v
+		}
+
+		visiting[u] = true
+		total := 0
+		for _, v := range graph[u] {
+			total += dfs(v, mask)
+		}
+
+		visiting[u] = false
+		memo[k] = total
+		return total
+	}
+	return dfs(start, 0)
+}
+
+func Run(filename string) (any, any) {
+	file, err := os.Open(filename)
+	if err != nil {
+		panic(err)
+	}
+	defer file.Close()
+
+	graph := make(map[string][]string)
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" {
+			continue
+		}
+		parts := strings.Split(line, ":")
+		if len(parts) != 2 {
+			continue
+		}
+		src := strings.TrimSpace(parts[0])
+		outs := strings.Fields(strings.TrimSpace(parts[1]))
+		graph[src] = outs
+	}
+
+	if err := scanner.Err(); err != nil {
+		panic(err)
+	}
+
+	part1 := Part1(graph)
+	part2 := Part2(graph)
+
+	return part1, part2
+}

2025/day11/day11_test.go

@@ -0,0 +1,35 @@
+package day11
+
+import (
+	"os"
+	"testing"
+)
+
+type TestCase struct {
+	FileName string
+	Part1    any
+	Part2    any
+}
+
+func TestDay11(t *testing.T) {
+	tests := []TestCase{
+		{"test.txt", 5, nil},
+		{"test2.txt", nil, 2},
+		{"input.txt", 634, 377452269415704},
+	}
+
+	for _, test := range tests {
+		if _, err := os.Stat(test.FileName); os.IsNotExist(err) {
+			t.Fatalf("test file does not exist: %v", test.FileName)
+		}
+
+		part1, part2 := Run(test.FileName)
+		if test.Part1 != nil && part1 != test.Part1 {
+			t.Fatalf("%s: unexpected part1:\nwant:\t%v\ngot:\t%v", test.FileName, test.Part1, part1)
+		}
+
+		if test.Part2 != nil && part2 != test.Part2 {
+			t.Fatalf("%s: unexpected part2:\nwant:\t%v\ngot:\t%v", test.FileName, test.Part2, part2)
+		}
+	}
+}

2025/day11/test.txt

@@ -0,0 +1,10 @@
+aaa: you hhh
+you: bbb ccc
+bbb: ddd eee
+ccc: ddd eee fff
+ddd: ggg
+eee: out
+fff: out
+ggg: out
+hhh: ccc fff iii
+iii: out

2025/day11/test2.txt

@@ -0,0 +1,13 @@
+svr: aaa bbb
+aaa: fft
+fft: ccc
+bbb: tty
+tty: ccc
+ccc: ddd eee
+ddd: hub
+hub: fff
+eee: dac
+dac: fff
+fff: ggg hhh
+ggg: out
+hhh: out