kt: add «1861. Rotating the Box»

URL:	https://leetcode.com/problems/rotating-the-box/
Signed-off-by: Matej Focko <me@mfocko.xyz>

kt/rotating-the-box.kt

@@ -0,0 +1,24 @@
+class Solution {
+    fun rotateTheBox(box: Array<CharArray>): Array<CharArray> {
+        val (rows, cols) = box.size to box[0].size
+        val rotated = Array(cols) { CharArray(rows) { '.' } }
+
+        (0..<rows).forEach { y ->
+            (0..<cols).reversed().fold(cols - 1) { lowestEmpty, x ->
+                when (box[y][x]) {
+                    '#' -> {
+                        rotated[lowestEmpty][rows - y - 1] = '#'
+                        lowestEmpty - 1
+                    }
+                    '*' -> {
+                        rotated[x][rows - y - 1] = '*'
+                        x - 1
+                    }
+                    else -> lowestEmpty
+                }
+            }
+        }
+
+        return rotated
+    }
+}