insert delete get random 1

https://leetcode.com/problems/insert-delete-getrandom-o1/?tab=Description

class RandomizedSet {
public:
    /** Initialize your data structure here. */

    vector<int> vec;
    map<int, int> hash;

    RandomizedSet() {
        srand(time(NULL));
    }

    /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
    bool insert(int val) {

        if(hash.find(val) != hash.end())
        {
            return false;
        }

        int index = vec.size();
        vec.push_back(val);
        hash[val] = index;

        return true;

    }

    /** Removes a value from the set. Returns true if the set contained the specified element. */
    bool remove(int val) {
        if(hash.find(val) == hash.end())
        {
            return false;
        }

        int index = hash[val];
        vec[index] = vec.back();
        hash[vec.back()] = index;
        vec.pop_back();
        hash.erase(val);
        return true;
    }

    /** Get a random element from the set. */
    int getRandom() {
        int size = vec.size();
        if(size == 0)
        {
            return 0;
        }

        return vec[rand()%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();
 */