day1

app/src/main/kotlin/org/day01/Day01.kt

@@ -0,0 +1,55 @@
+
+package org.example
+
+import kotlin.io.println
+import kotlin.math.abs
+
+class Day01 {
+    fun parse(input: String): List<List<Int>> {
+        val lhs: MutableList<Int> = mutableListOf()
+        val rhs: MutableList<Int> = mutableListOf()
+
+        for (line in input.lines()) {
+            val split = line.split("   ").map { str -> str.toInt() }
+            lhs.add(split[0])
+            rhs.add(split[1])
+        }
+
+        return listOf(lhs, rhs)
+    }
+
+    fun part1(input: String): Int {
+        val lists = parse(input)
+        val lhs = lists[0].sorted()
+        val rhs = lists[1].sorted()
+
+        var sum = 0
+        for (i in 0..<lhs.count()) {
+            sum += abs(lhs[i] - rhs[i])
+        }
+        return sum;
+    }
+
+    fun part2(input: String): Int {
+        val lists = parse(input)
+        val lhs = lists[0].sorted()
+        val rhs = lists[1].sorted()
+
+        var sum = 0
+        for (i in 0..<lhs.count()) {
+            var rhs_idx = 0
+            val target = lhs[i]
+            var count = 0
+            while (rhs[rhs_idx] < target) {
+                rhs_idx += 1
+            }
+            while (rhs[rhs_idx] == target) {
+                count += 1
+                rhs_idx += 1
+            }
+
+            sum += target * count
+        }
+        return sum
+    }
+}

app/src/main/kotlin/org/example/App.kt

@@ -0,0 +1,15 @@
+/*
+ * This source file was generated by the Gradle 'init' task
+ */
+package org.example
+
+class App {
+    val greeting: String
+        get() {
+            return "Hello World!"
+        }
+}
+
+fun main() {
+    println(App().greeting)
+}

app/src/test/kotlin/org/day01/Day01Test.kt

@@ -0,0 +1,36 @@
+package org.example
+
+import kotlin.test.Test
+import kotlin.test.assertNotNull
+import kotlin.test.assertIs
+
+class Day01Test {
+    @Test fun part1() {
+        val day = Day01()
+        val test = """3   4
+4   3
+2   5
+1   3
+3   9
+3   3"""
+
+        val output = day.part1(test)
+        println(output)
+        assert(output == 11)
+    }
+
+    @Test fun part2() {
+        val day = Day01()
+
+        val test =  """3   4
+4   3
+2   5
+1   3
+3   9
+3   3"""
+
+        val output = day.part2(test)
+        println(output)
+        assert(output == 31)
+    }
+}

app/src/test/kotlin/org/example/AppTest.kt

@@ -0,0 +1,14 @@
+/*
+ * This source file was generated by the Gradle 'init' task
+ */
+package org.example
+
+import kotlin.test.Test
+import kotlin.test.assertNotNull
+
+class AppTest {
+    @Test fun appHasAGreeting() {
+        val classUnderTest = App()
+        assertNotNull(classUnderTest.greeting, "app should have a greeting")
+    }
+}