add prob #898(2nd)

Author: randomwalk10

Diff for: 898_Bitwise_ORs_of_Subarrays_2nd.cpp

@@ -0,0 +1,27 @@
+/* O(N^2) in time and O(N^2) in space
+ *
+ * Could be N^2 in the worst scenario.
+ * but this method is faster than the first one in practice
+ */
+
+#include <vector>
+#include <unordered_set>
+using namespace std;
+
+class Solution {
+public:
+    int subarrayBitwiseORs(vector<int>& A) {
+        unordered_set<int> res;
+
+        for(int i=0; i<(int)A.size(); ++i){
+            res.insert(A[i]);
+            for(int j=i-1; j>=0; --j){
+                if((A[j]|A[i])==A[j]) break;
+                A[j] |= A[i];
+                res.insert(A[j]);
+            }
+        }
+
+        return res.size();
+    }
+};