kt: add «2570. Merge Two 2D Arrays by Summing Values»

URL:	https://leetcode.com/problems/merge-two-2d-arrays-by-summing-values/
Signed-off-by: Matej Focko <me@mfocko.xyz>

kt/merge-two-2d-arrays-by-summing-values.kt

@@ -0,0 +1,39 @@
+class Solution {
+    fun mergeArrays(
+        nums1: Array<IntArray>,
+        nums2: Array<IntArray>,
+    ): Array<IntArray> {
+        val (n, m) = nums1.size to nums2.size
+        var (i, j) = 0 to 0
+
+        val result: MutableList<IntArray> = mutableListOf()
+        while (i < n && j < m) {
+            when {
+                nums1[i][0] == nums2[j][0] -> {
+                    result.add(intArrayOf(nums1[i][0], nums1[i][1] + nums2[j][1]))
+                    i++
+                    j++
+                }
+                nums1[i][0] < nums2[j][0] -> {
+                    result.add(nums1[i])
+                    i++
+                }
+                else -> {
+                    result.add(nums2[j])
+                    j++
+                }
+            }
+        }
+
+        while (i < n) {
+            result.add(nums1[i])
+            i++
+        }
+        while (j < m) {
+            result.add(nums2[j])
+            j++
+        }
+
+        return result.toTypedArray()
+    }
+}