create 0380-insert-delete-getrandom-o1

Author: Maunish-dave

cpp/0380-insert-delete-getrandom-o1.cpp

@@ -0,0 +1,57 @@
+class RandomizedSet {
+public:
+
+    unordered_map<int,int> indices;
+    vector<int> values;
+    RandomizedSet() {
+    }
+    
+    bool insert(int val) {
+
+        if(indices.find(val)==indices.end()){
+            values.push_back(val);
+            // store the index of that value
+            indices[val] = values.size() -1;
+            return true;
+        }
+        return false;
+    }
+    
+    bool remove(int val) {
+
+       if(indices.find(val)==indices.end()){
+           return false;
+       }
+
+        // find index of the value
+        int idx = indices[val];
+        // get the last value in the vector
+        // and change its index to curr val's index
+        indices[values[values.size()-1]] = idx;
+
+        // replace curr vals index with last 
+        // last value
+        values[idx] = values[values.size()-1];
+
+        // so now the curr val is removed from the
+        // vector replaced by last value and so 
+        // we could just remove last value 
+        values.pop_back();
+
+        // also erase it from the hash map
+        indices.erase(val);
+        return true;
+    }
+    
+    int getRandom() {
+        return values[rand()%values.size()];
+    }
+};
+
+/**
+ * Your RandomizedSet object will be instantiated and called as such:
+ * RandomizedSet* obj = new RandomizedSet();
+ * bool param_1 = obj->insert(val);
+ * bool param_2 = obj->remove(val);
+ * int param_3 = obj->getRandom();
+ */