kt: add «1671. Minimum Number of Removals to Make Mountain Array»

URL:	https://leetcode.com/problems/minimum-number-of-removals-to-make-mountain-array/

kt/minimum-number-of-removals-to-make-mountain-array.kt

@@ -0,0 +1,38 @@
+class Solution {
+    private fun longestIncreasing(nums: IntArray): IntArray {
+        val found =
+            IntArray(nums.size) {
+                1
+            }
+
+        nums.indices
+            .flatMap { i ->
+                (0..i - 1)
+                    .reversed()
+                    .map { j -> i to j }
+            }
+            .filter { (i, j) -> nums[i] > nums[j] }
+            .forEach { (i, j) ->
+                found[i] = listOf(found[i], 1 + found[j]).max()
+            }
+
+        return found
+    }
+
+    fun minimumMountainRemovals(nums: IntArray): Int {
+        val increasing = longestIncreasing(nums)
+
+        nums.reverse()
+        val decreasing = longestIncreasing(nums)
+        decreasing.reverse()
+
+        return increasing
+            .zip(decreasing)
+            .filter { (l, r) ->
+                l > 1 && r > 1
+            }
+            .minOf { (l, r) ->
+                nums.size - l - r + 1
+            } ?: nums.size
+    }
+}