kt: add «2161. Partition Array According to Given Pivot»

URL:	https://leetcode.com/problems/partition-array-according-to-given-pivot/
Signed-off-by: Matej Focko <me@mfocko.xyz>

kt/partition-array-according-to-given-pivot.kt

@@ -0,0 +1,28 @@
+class Solution {
+    fun pivotArray(
+        nums: IntArray,
+        pivot: Int,
+    ): IntArray {
+        val res = IntArray(nums.size)
+
+        var (smaller, greater) = 0 to nums.size - 1
+        nums.indices.map { i -> i to nums.size - 1 - i }.forEach { (i, j) ->
+            if (nums[i] < pivot) {
+                res[smaller] = nums[i]
+                smaller++
+            }
+
+            if (nums[j] > pivot) {
+                res[greater] = nums[j]
+                greater--
+            }
+        }
+
+        while (smaller <= greater) {
+            res[smaller] = pivot
+            smaller++
+        }
+
+        return res
+    }
+}