Move year 2021 into a subfolder

1 files changed, 27 insertions, 0 deletions

diff --git a/2021-kotlin/src/Day07.kt b/2021-kotlin/src/Day07.kt
new file mode 100644
index 0000000..9c1b79f
--- /dev/null
+++ b/2021-kotlin/src/Day07.kt
@@ -0,0 +1,27 @@
+import kotlin.math.absoluteValue
+
+object Day07 {
+    fun part1(input: String): Int {
+        val numbers = input.trim().split(",").map(String::toInt)
+        val range = numbers.minOrNull()!!..numbers.maxOrNull()!!
+
+        return range.minOf { n -> numbers.sumOf { (it - n).absoluteValue } }
+    }
+
+    fun part2(input: String): Int {
+        val numbers = input.trim().split(",").map(String::toInt)
+        val range = numbers.minOrNull()!!..numbers.maxOrNull()!!
+
+        return range.minOf { n -> numbers.map { (it - n).absoluteValue }.sumOf { (it * (it + 1)) / 2 } }
+    }
+}
+
+fun main() {
+    val testInput = readInputAsString("Day07_test")
+    check(Day07.part1(testInput) == 37)
+    check(Day07.part2(testInput) == 168)
+
+    val input = readInputAsString("Day07")
+    println(Day07.part1(input))
+    println(Day07.part2(input))
+}