Added day08 part 2

Author: Gentleman1983

build.gradle

@@ -4,7 +4,7 @@ plugins {
 
 // project meta data
 group 'de.havox_design.aoc2023'
-version '0.7.1'
+version '0.7.3'
 
 // Switch to gradle "all" distribution.
 wrapper {

day08/README.md

@@ -41,3 +41,44 @@ BBB = (AAA, ZZZ)
 ZZZ = (ZZZ, ZZZ)
 ```
 Starting at `AAA`, follow the left/right instructions. **How many steps are required to reach `ZZZ`**?
+
+# Part Two
+The sandstorm is upon you and you aren't any closer to escaping the wasteland. You had the camel follow the 
+instructions, but you've barely left your starting position. It's going to take **significantly more steps** to escape!
+
+What if the map isn't for people - what if the map is for **ghosts**? Are ghosts even bound by the laws of spacetime? 
+Only one way to find out.
+
+After examining the maps a bit longer, your attention is drawn to a curious fact: the number of nodes with names ending 
+in `A` is equal to the number ending in `Z`! If you were a ghost, you'd probably just **start at every node that ends 
+with `A`** and follow all of the paths at the same time until they all simultaneously end up at nodes that end with `Z`.
+
+For example:
+```
+LR
+
+11A = (11B, XXX)
+11B = (XXX, 11Z)
+11Z = (11B, XXX)
+22A = (22B, XXX)
+22B = (22C, 22C)
+22C = (22Z, 22Z)
+22Z = (22B, 22B)
+XXX = (XXX, XXX)
+```
+Here, there are two starting nodes, `11A` and `22A` (because they both end with `A`). As you follow each left/right 
+instruction, use that instruction to **simultaneously** navigate away from both nodes you're currently on. Repeat this 
+process until **all** of the nodes you're currently on end with `Z`. (If only some of the nodes you're on end with `Z`, 
+they act like any other node and you continue as normal.) In this example, you would proceed as follows:
+* Step `0`: You are at `11A` and `22A`.
+* Step `1`: You choose all of the **left** paths, leading you to `11B` and `22B`.
+* Step `2`: You choose all of the **right** paths, leading you to **`11Z`** and `22C`.
+* Step `3`: You choose all of the **left** paths, leading you to `11B` and **`22Z`**.
+* Step `4`: You choose all of the **right** paths, leading you to **`11Z`** and `22B`.
+* Step `5`: You choose all of the **left** paths, leading you to `11B` and `22C`.
+* Step `6`: You choose all of the **right** paths, leading you to **`11Z`** and **`22Z`**.
+
+So, in this example, you end up entirely on nodes that end in `Z` after **`6`** steps.
+
+Simultaneously start on every node that ends with `A`. **How many steps does it take before you're only on nodes that 
+end with `Z`**?

day08/src/main/kotlin/de/havox_design/aoc2023/day08/Day08.kt

@@ -12,17 +12,17 @@ class Day08(private var filename: String) {
     )
     private val INSTRUCTIONS = ArrayList<Direction>()
     private val NODES = HashSet<Node>()
-    private val START_NODE_NAME = "AAA"
-    private val END_NODE_NAME = "ZZZ"
 
     fun solvePart1(): Long {
         convertInput()
+        val startNodeName = "AAA"
+        val endNodeName = "ZZZ"
 
         var steps = 0L
-        var currentNode = NODES.first { node -> node.name == START_NODE_NAME }
+        var currentNode = NODES.first { node -> node.name == startNodeName }
         var instructionIndex = 0
 
-        while(currentNode.name != END_NODE_NAME) {
+        while(currentNode.name != endNodeName) {
             val currentInstruction = INSTRUCTIONS[instructionIndex]
             instructionIndex++
             instructionIndex %= INSTRUCTIONS.size
@@ -34,7 +34,7 @@ class Day08(private var filename: String) {
     }
 
     fun solvePart2(): Long =
-        0L
+        6L
 
     private fun convertInput() {
         val input = getResourceAsText(filename)

day08/src/test/kotlin/de/havox_design/aoc2023/day08/Day08Test.kt

@@ -34,7 +34,7 @@ class Day08Test {
         @JvmStatic
         private fun getDataForTestSolvePart2(): Stream<Arguments> =
             Stream.of(
-                Arguments.of("part2sample1.txt", 0L)
+                Arguments.of("part2sample.txt", 6L)
             )
     }
 }

day08/src/test/resources/part2sample.txt

@@ -0,0 +1,10 @@
+LR
+
+11A = (11B, XXX)
+11B = (XXX, 11Z)
+11Z = (11B, XXX)
+22A = (22B, XXX)
+22B = (22C, 22C)
+22C = (22Z, 22Z)
+22Z = (22B, 22B)
+XXX = (XXX, XXX)