create 0380-insert-delete-getrandom-o1

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();
+ */