class RandomizedSet {
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(m_map.find(val) != m_map.end())
            return false;
        m_nums.push_back(val);
        int len = m_nums.size();
        m_map[val] = len - 1;
        return true;
    }
    
    /** Removes a value from the set. Returns true if the set contained the specified element. */
    bool remove(int val) {
        if(m_map.find(val) == m_map.end())
            return false;
        int idx = m_map[val], len = m_nums.size(), num = m_nums[len - 1];
        swap(m_nums[idx], m_nums[len - 1]);
        m_nums.pop_back();
        m_map.erase(val);
        if(idx != len - 1)m_map[num] = idx;
        return true;
    }
    
    /** Get a random element from the set. */
    int getRandom() {
        if(m_nums.empty())return 0;
        int len = m_nums.size(), random = rand() % len;
        return m_nums[random];
    }
    
private:
    
    unordered_map<int, int> m_map;
    vector<int> m_nums;
};

/**
 * 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();
 */