Create 1671. Minimum Number of Removals to Make Mountain Array (#621)

Author: Chayandas07

1671. Minimum Number of Removals to Make Mountain Array

@@ -0,0 +1,48 @@
+class Solution {
+public:
+    int lis(int i, vector<int>& nums, vector<int>& dp) {
+        if (dp[i] != -1)
+            return dp[i];
+        int maxi = 1;
+        for (int j = 0; j < i; j++) {
+            if (nums[i] > nums[j]) {
+                maxi = max(maxi, lis(j, nums, dp) + 1);
+            }
+        }
+        return dp[i] = maxi;
+    }
+    int lds(int i, vector<int>& nums, vector<int>& dp) {
+        if (dp[i] != -1)
+            return dp[i];
+        int maxi = 1;
+        for (int j = i + 1; j < nums.size(); j++) {
+            if (nums[i] > nums[j]) {
+                maxi = max(maxi, lds(j, nums, dp) + 1);
+            }
+        }
+        return dp[i] = maxi;
+    }
+
+    int minimumMountainRemovals(vector<int>& nums) {
+        int n = nums.size();
+        if (n < 3)
+            return 0;
+        vector<int> lisOfAllIndices(n, -1);
+        vector<int> ldsOfAllIndices(n, -1);
+
+        for (int i = 0; i < n; i++) 
+        lis(i, nums, lisOfAllIndices);
+        
+        for (int i = n - 1; i >= 0; i--) 
+        lds(i, nums, ldsOfAllIndices);
+        
+
+        int maxi = 0;
+        for (int i = 1; i < n - 1; i++) {
+            if (lisOfAllIndices[i] > 1 && ldsOfAllIndices[i] > 1) { 
+                maxi = max(maxi, lisOfAllIndices[i] + ldsOfAllIndices[i] - 1);
+            }
+        }
+        return n - maxi;
+    }
+};