Day 6 (finally got time)

src/main/kotlin/com/basdado/adventofcode/day5/Day5.kt

@@ -165,5 +165,5 @@ object Day5 {
 
     data class OperationResult(val moveToNextInstruction: Boolean = true, val output: Int? = null)
 
-    val VOID = OperationResult()
+    private val VOID = OperationResult()
 }

src/main/kotlin/com/basdado/adventofcode/day6/Day6.kt

@@ -0,0 +1,77 @@
+package com.basdado.adventofcode.day6
+
+import com.basdado.adventofcode.lines
+
+const val DAY6_INPUT_PATH = "/day/6/input.txt"
+
+
+fun main() {
+    Day6.puzzle1()
+    Day6.puzzle2()
+}
+
+object Day6 {
+
+    fun puzzle1() {
+        // orbits is a map from names to the objects they are orbiting
+        val orbits = loadOrbits()
+        val cache = mutableMapOf<String, Int>()
+        println(orbits.keys.stream()
+//            .peek{ println("${calculateOrbitCount(it, orbits, cache)} orbit in $it")}
+            .mapToInt { calculateOrbitCount(it, orbits, cache) }
+            .sum())
+    }
+
+    fun puzzle2() {
+
+        val orbits = loadOrbits()
+        val youToRoot = pathToRoot("YOU", orbits).reversed()
+        val sanToRoot = pathToRoot("SAN", orbits).reversed()
+
+        println(youToRoot)
+        println(sanToRoot)
+
+        val overlapLength = youToRoot.indexOfLast { sanToRoot.contains(it) } + 1
+        println((youToRoot.size - 1 - overlapLength) + (sanToRoot.size - 1 - overlapLength))
+
+    }
+
+    private fun loadOrbits(): Map<String, String> {
+        val orbits = mutableMapOf<String, String>()
+        lines(DAY6_INPUT_PATH)
+            .forEach {
+                val split = it.indexOf(")")
+                val o1 = it.substring(0, split)
+                val o2 = it.substring(split + 1)
+                orbits[o2] = o1
+            }
+        return orbits
+    }
+
+    private fun calculateOrbitCount(o: String, orbits: Map<String, String>, cache: MutableMap<String, Int>): Int {
+
+        val parent = orbits[o]
+        val res = if (parent == null) {
+            0
+        } else {
+            1 + (cache[parent] ?: calculateOrbitCount(parent, orbits, cache))
+        }
+        cache[o] = res
+        return res
+    }
+
+    private fun pathToRoot(source: String, orbits: Map<String, String>): List<String> {
+
+        val parent = orbits[source]
+        return if (parent == null) {
+            listOf(source)
+        } else {
+            listOf(source) + pathToRoot(parent, orbits)
+        }
+    }
+
+    data class SpaceObject (
+        val name: String,
+        val parent: SpaceObject? = null
+    )
+}

src/main/resources/day/6/ex1.txt

@@ -0,0 +1,11 @@
+COM)B
+B)C
+C)D
+D)E
+E)F
+B)G
+G)H
+D)I
+E)J
+J)K
+K)L

src/main/resources/day/6/ex2.txt

@@ -0,0 +1,13 @@
+COM)B
+B)C
+C)D
+D)E
+E)F
+B)G
+G)H
+D)I
+E)J
+J)K
+K)L
+K)YOU
+I)SAN