Create minimum-number-of-removals-to-make-mountain-array.cpp

Author: kamyu104

C++/minimum-number-of-removals-to-make-mountain-array.cpp

@@ -0,0 +1,31 @@
+// Time:  O(nlogn)
+// Space: O(n)
+
+class Solution {
+public:
+    int minimumMountainRemovals(vector<int>& nums) {
+        vector<int> left_lis_len(size(nums));
+        vector<int> lis;
+        for (int i = 0; i + 1 < size(nums); ++i) {
+            auto it = lower_bound(begin(lis), end(lis), nums[i]);
+            left_lis_len[i] = distance(begin(lis), it);
+            if (it == end(lis)) {
+                lis.emplace_back(nums[i]);
+            } else {
+                *it = nums[i];
+            }
+        }
+        lis.clear();
+        int max_len = 0;
+        for (int i = size(nums) - 1; i > 0; --i) {
+            auto it = lower_bound(begin(lis), end(lis), nums[i]);
+            max_len = max(max_len, left_lis_len[i] + int(distance(begin(lis), it)));
+            if (it == end(lis)) {
+                lis.emplace_back(nums[i]);
+            } else {
+                *it = nums[i];
+            }
+        }
+        return size(nums) - (1 + max_len);
+    }
+};