2024 day 1

2024/src/main/kotlin/day1.kt

@@ -0,0 +1,40 @@
+import kotlin.math.abs
+
+fun main() {
+    val input = object {}.javaClass.getResourceAsStream("day1.txt")
+        ?.bufferedReader()
+        ?.lineSequence()
+        ?: error("Cannot read input")
+
+    val a = mutableListOf<Int>()
+    val b = mutableListOf<Int>()
+
+    val spaces = "\\s+".toRegex()
+
+    for (line in input) {
+        val parts = line.split(spaces, limit = 2)
+        val (first, second) = parts
+        a.add(first.toInt())
+        b.add(second.toInt())
+    }
+
+    assert(a.size == b.size)
+    a.sort()
+    b.sort()
+
+    var sum = 0
+    for (index in a.indices) {
+        sum += abs(a[index] - b[index])
+    }
+
+    println("Part 1: $sum")
+
+
+    sum = 0
+
+    for (value in a) {
+        sum += value * b.count { it == value }
+    }
+
+    println("Part 2: $sum")
+}