Insert Delete GetRandom O(1)

[fkdl0048]

class RandomizedSet {
public:
    RandomizedSet() {}
    
    bool insert(int val) {
        if (valToIndex.find(val) != valToIndex.end()) {
            return false;
        }

        values.push_back(val);
        valToIndex[val] = values.size() - 1;

        return true;
    }
    
    bool remove(int val) {
        if (valToIndex.find(val) == valToIndex.end()) {
            return false;
        }

        int lastElement = values.back();
        int indexToRemove = valToIndex[val];

        values[indexToRemove] = lastElement;
        valToIndex[lastElement] = indexToRemove;

        values.pop_back();
        valToIndex.erase(val);

        return true;
    }
    
    int getRandom() {
        int randomindex = rand() % values.size();
        return values[randomindex];
    }

private:
    unordered_map<int, int> valToIndex;
    vector<int> values;
};

/**
 * 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();
 */