1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
|
object Day12 {
private class CaveGraph {
companion object {
fun fromLines(input: List<String>): CaveGraph =
CaveGraph().apply { input.forEach { addConnection(it) } }
}
private val adjacencyList = mutableMapOf<Node, Set<Node>>()
private fun addConnection(connectionString: String) {
val (from, to) = connectionString.split("-").map(Node::fromString)
adjacencyList.merge(from, setOf(to), Set<Node>::union)
adjacencyList.merge(to, setOf(from), Set<Node>::union)
}
fun countPaths(canUseDoubleTraversal: Boolean = false): Int =
traverse(Node.Start, setOf(), !canUseDoubleTraversal)
private fun traverse(from: Node, visitedBefore: Set<Node>, usedUpDoubleTraverse: Boolean): Int {
return adjacencyList[from]!!.sumOf {
when (it) {
is Node.Start -> 0
is Node.End -> 1
is Node.Big -> traverse(it, visitedBefore + from, usedUpDoubleTraverse)
is Node.Small -> {
if (!visitedBefore.contains(it)) {
traverse(it, visitedBefore + from, usedUpDoubleTraverse)
} else if (!usedUpDoubleTraverse) {
traverse(it, visitedBefore + from, true)
} else {
0
}
}
}
}
}
private sealed class Node {
companion object {
fun fromString(text: String): Node = when (text) {
"start" -> Start
"end" -> End
else -> if (text == text.uppercase()) {
Big(text)
} else {
Small(text)
}
}
}
object Start : Node()
object End : Node()
data class Small(private val identifier: String) : Node()
data class Big(private val identifier: String) : Node()
}
}
fun bothParts(input: List<String>) = CaveGraph.fromLines(input).let { it.countPaths() to it.countPaths(true) }
}
fun main() {
val testInput = readInputAsLines("Day12_test")
val testOutput = Day12.bothParts(testInput)
check(testOutput.first == 226)
check(testOutput.second == 3509)
val input = readInputAsLines("Day12")
val output = Day12.bothParts(input)
println(output.first)
println(output.second)
}
|