Implement day 10, in Kotlin

2017/day-10/solution.kt

@@ -0,0 +1,68 @@
+fun valArray(): IntArray
+{
+    val arr = IntArray(256)
+    for (i in arr.indices) {
+        arr[i] = i
+    }
+
+    return arr
+}
+
+fun hash(input: IntArray, values: IntArray, index: Int, skip: Int): Pair<Int, Int> {
+    var curIndex = index
+    var curSkip = skip
+    for (range in input) {
+        val halfRange = range / 2
+
+        for (i in 0..(halfRange - 1)) {
+            val i1 = (curIndex + i) % values.size
+            val i2 = (curIndex + range - i - 1) % values.size
+
+            values[i1] = values[i2].also { values[i2] = values[i1] }
+        }
+
+        curIndex = (curIndex + range + curSkip) % values.size
+        curSkip++
+    }
+
+    return Pair(curIndex, curSkip)
+}
+
+fun solve(input: String)
+{
+    // Part 1
+    val part1input = input.split(",").map { it.toInt() }.toIntArray()
+    val values = valArray()
+    hash(part1input, values, 0, 0)
+    println(values[0] * values[1])
+
+    // Part 2
+    val part2input = ArrayList(List(input.length) { input[it].toInt()})
+    part2input.addAll(arrayOf(17, 31, 73, 47, 23))
+
+    val values2 = valArray()
+    var skip = 0
+    var index = 0
+
+    // Repeat hash 64 times
+    for (i in 1..64) {
+        val (newIndex, newSkip) = hash(part2input.toIntArray(), values2, index, skip)
+        index = newIndex
+        skip = newSkip
+    }
+
+    for (i in 0..15) {
+        val startIndex = 16 * i
+        val endIndex = startIndex + 15
+
+        val currentNum = values2.slice(startIndex..endIndex).reduce{a, b -> a.xor(b)}
+        print("%02x".format(currentNum))
+    }
+    println()
+
+}
+
+fun main(args: Array<String>)
+{
+    solve(readLine()!!)
+}