class RandomizedSet {
unordered_map<int,int> hash;
vector<int> vec;
public:
/** Initialize your data structure here. */
RandomizedSet() {}
/** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
bool insert(int val) {
if(hash.count(val))
return false;
vec.push_back(val);
hash[val] = vec.size()-1;
return true;
}
/** Removes a value from the set. Returns true if the set contained the specified element. */
bool remove(int val) {
if(!hash.count(val))
return false;
hash[vec.back()] = hash[val];
swap(vec.back(),vec[hash[val]]);
vec.pop_back();
hash.erase(val);
return true;
}
/** Get a random element from the set. */
int getRandom() {
if(vec.empty()) return 0;
return vec[rand()%vec.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();
*/