Day 1

src/Day01.kt

@@ -1,21 +1,47 @@
+import kotlin.math.abs
+
+data class LocationLists(val left: List<Int>, val right: List<Int>)
+
 fun main() {
+    fun getLocationLists(input: List<String>): LocationLists {
+        val leftList = mutableListOf<Int>()
+        val rightList = mutableListOf<Int>()
+
+        input.forEach {
+            val splits = it.split(Regex("\\s+"),2)
+            leftList.add(splits[0].toInt())
+            rightList.add(splits[1].toInt())
+        }
+
+        return LocationLists(leftList.sorted(), rightList.sorted())
+    }
+
     fun part1(input: List<String>): Int {
-        return input.size
+
+        val locationLists = getLocationLists(input)
+
+        return locationLists.left.foldIndexed(0) {index, acc, elt ->
+            val distance = abs(elt-locationLists.right[index])
+            distance + acc
+        }
     }
 
     fun part2(input: List<String>): Int {
-        return input.size
-    }
+        val locationLists = getLocationLists(input)
 
-    // Test if implementation meets criteria from the description, like:
-    check(part1(listOf("test_input")) == 1)
+        return locationLists.left.fold(0) { acc, elt ->
+            val similarityScore = elt * locationLists.right.count { it == elt }
+            similarityScore + acc
+        }
+    }
 
     // Or read a large test input from the `src/Day01_test.txt` file:
     val testInput = readInput("Day01_test")
-    check(part1(testInput) == 1)
-
-    // Read the input from the `src/Day01.txt` file.
     val input = readInput("Day01")
+
+    check(part1(testInput) == 11)
     part1(input).println()
+
+    check(part2(testInput) == 31)
     part2(input).println()
 }

src/_template.kt

@@ -0,0 +1,18 @@
+fun main() {
+    fun part1(input: List<String>): Int {
+        return input.size
+    }
+
+    fun part2(input: List<String>): Int {
+        return input.size
+    }
+
+    val testInput = readInput("DayXX_test")
+    val input = readInput("DayXX")
+
+    check(part1(testInput) == 1)
+    part1(input).println()
+
+    check(part2(testInput) == 1)
+    part2(input).println()
+}