kt: add «2698. Find the Punishment Number of an Integer»

URL:	https://leetcode.com/problems/find-the-punishment-number-of-an-integer/
Signed-off-by: Matej Focko <me@mfocko.xyz>

kt/find-the-punishment-number-of-an-integer.kt

@@ -0,0 +1,28 @@
+class Solution {
+    companion object {
+        private val PARTITIONS: List<Int> = listOf(10, 100, 1000)
+    }
+
+    private fun canPartition(
+        num: Int,
+        target: Int,
+    ): Boolean =
+        when {
+            target < 0 || num < target -> false
+            num == target -> true
+            else ->
+                PARTITIONS.any { it ->
+                    canPartition(num / it, target - num % it)
+                }
+        }
+
+    fun punishmentNumber(n: Int): Int =
+        (1..n).asSequence().sumOf {
+            val square = it * it
+
+            when {
+                canPartition(square, it) -> square
+                else -> 0
+            }
+        }
+}