Day 12

12/input.txt

@@ -0,0 +1,22 @@
+zi-end
+XR-start
+zk-zi
+TS-zk
+zw-vl
+zk-zw
+end-po
+ws-zw
+TS-ws
+po-TS
+po-YH
+po-xk
+zi-ws
+zk-end
+zi-XR
+XR-zk
+vl-TS
+start-zw
+vl-start
+XR-zw
+XR-vl
+XR-ws

12/main.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"log"
+	"os"
+	"strings"
+
+	"github.com/thoas/go-funk"
+)
+
+func main() {
+	inputBytes, _ := os.ReadFile("input.txt")
+	input := strings.Split(string(inputBytes), "\n")
+
+	log.Println("Puzzle 1:", puzzle1(input))
+	log.Println("Puzzle 2:", puzzle2(input))
+}
+
+func puzzle1(input []string) int {
+	return do(input, false)
+}
+
+func puzzle2(input []string) int {
+	return do(input, true)
+}
+
+func do(input []string, puzzle2 bool) int {
+	connections := map[string][]string{}
+	// Read input
+	for _, line := range input {
+		split := strings.Split(line, "-")
+		connections[split[0]] = append(connections[split[0]], split[1])
+		connections[split[1]] = append(connections[split[1]], split[0])
+	}
+	// Find all routes from start to end
+	return len(route(puzzle2, connections, []string{"start"}, false))
+}
+
+func route(puzzle2 bool, connections map[string][]string, visited []string, smallTwice bool) (routes [][]string) {
+	// Find all routes from last visited to end
+	for _, next := range connections[visited[len(visited)-1]] {
+		// Check if next is end
+		if next == "end" {
+			routes = append(routes, append(visited, next))
+			continue
+		}
+		// Can visit a single small cave twice, but all remaining caves once
+		if next[0] >= 'a' && next[0] <= 'z' && funk.ContainsString(visited, next) {
+			if next != "start" && puzzle2 && !smallTwice {
+				routes = append(routes, route(puzzle2, connections, append(visited, next), true)...)
+			}
+			continue
+		}
+		// Check next possible routes
+		routes = append(routes, route(puzzle2, connections, append(visited, next), smallTwice)...)
+	}
+	// Return all found routes
+	return routes
+}

12/main_test.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test(t *testing.T) {
+	// Test 1
+
+	inputBytes, _ := os.ReadFile("test1.txt")
+	input := strings.Split(string(inputBytes), "\n")
+
+	assert.Equal(t, 10, puzzle1(input))
+	assert.Equal(t, 36, puzzle2(input))
+
+	// Test 2
+
+	inputBytes, _ = os.ReadFile("test2.txt")
+	input = strings.Split(string(inputBytes), "\n")
+
+	assert.Equal(t, 19, puzzle1(input))
+	assert.Equal(t, 103, puzzle2(input))
+
+	// Test 3
+
+	inputBytes, _ = os.ReadFile("test3.txt")
+	input = strings.Split(string(inputBytes), "\n")
+
+	assert.Equal(t, 226, puzzle1(input))
+	assert.Equal(t, 3509, puzzle2(input))
+}

12/test1.txt

@@ -0,0 +1,7 @@
+start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end

12/test2.txt

@@ -0,0 +1,10 @@
+dc-end
+HN-start
+start-kj
+dc-start
+dc-HN
+LN-dc
+HN-end
+kj-sa
+kj-HN
+kj-dc

12/test3.txt

@@ -0,0 +1,18 @@
+fs-end
+he-DX
+fs-he
+start-DX
+pj-DX
+end-zg
+zg-sl
+zg-pj
+pj-he
+RW-he
+fs-DX
+pj-RW
+zg-RW
+start-pj
+he-WI
+zg-he
+pj-fs
+start-RW