Solution.cpp

class RandomizedSet {
public:
    RandomizedSet() {
    }

    bool insert(int val) {
        if (d.count(val)) {
            return false;
        }
        d[val] = q.size();
        q.push_back(val);
        return true;
    }

    bool remove(int val) {
        if (!d.count(val)) {
            return false;
        }
        int i = d[val];
        d[q.back()] = i;
        q[i] = q.back();
        q.pop_back();
        d.erase(val);
        return true;
    }

    int getRandom() {
        return q[rand() % q.size()];
    }

private:
    unordered_map<int, int> d;
    vector<int> q;
};

/**
 * 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();
 */