Insert Delete GetRandom O(1) - Duplicates allowed Solutions in C++

// Source : https://leetcode.com/problems/insert-delete-getrandom-o1-duplicates-allowed/
// Author : Hao Chen
// Date   : 2016-08-25



class RandomizedCollection {
public:
    /** Initialize your data structure here. */
    RandomizedCollection() {
        srand(time(NULL));
    }
    
    /** Inserts a value to the collection. Returns true if the collection did not already contain the specified element. */
    bool insert(int val) {
        data.push_back(val);
        valpos[val].insert( data.size() - 1 );
        return (valpos[val].size() == 1);
    }
    
    /** Removes a value from the collection. Returns true if the collection contained the specified element. */
    bool remove(int val) {
        // not found
        if (!find(val)) return false;
        
        
        //same idea with non-duplication version, but need be careful with some edge case
        int _idx = *(valpos[val].begin());
        int _val = data.back();
        
        valpos[_val].insert(_idx);
        data[_idx] = _val;
        
        valpos[val].erase(_idx);
        if (valpos[val].size()==0){
            valpos.erase(val);
        }
        
        data.pop_back();
        if ( _idx < data.size() ){
            valpos[_val].erase(data.size());
            valpos[_val].insert(_idx);
        }
        
        return true;        
    }
    
    /** Get a random element from the collection. */
    int getRandom() {
        return data[ rand() % data.size() ];
    }
private:
    unordered_map<int, unordered_set<int>> valpos; //value position map
    vector<int> data;
    bool find(int val) {
        return (valpos.find(val) != valpos.end());
    }
   
};

/**
 * Your RandomizedCollection object will be instantiated and called as such:
 * RandomizedCollection obj = new RandomizedCollection();
 * bool param_1 = obj.insert(val);
 * bool param_2 = obj.remove(val);
 * int param_3 = obj.getRandom();
 */

/// Source : https://leetcode.com/problems/insert-delete-getrandom-o1-duplicates-allowed/description/
/// Author : liuyubobobo
/// Time   : 2018-07-08

#include <iostream>
#include <vector>
#include <unordered_map>
#include <unordered_set>

using namespace std;

/// Vector to stroe all elements
/// HashMap to restore all maps between elements and index
/// Time Complexity: O(1)
/// Space Complexity: O(n)
class RandomizedCollection {

private:
    vector<int> nums;
    unordered_map<int, unordered_set<int>> indexes;

public:
    /** Initialize your data structure here. */
    RandomizedCollection() {
        nums.clear();
        indexes.clear();
    }

    /** Inserts a value to the collection. Returns true if the collection did not already contain the specified element. */
    bool insert(int val) {
        nums.push_back(val);
        indexes[val].insert(nums.size() - 1);

        return indexes[val].size() == 1;
    }

    /** Removes a value from the collection. Returns true if the collection contained the specified element. */
    bool remove(int val) {
        if(indexes.find(val) != indexes.end()){
            int i = *indexes[val].begin();
            indexes[val].erase(i);
            if(indexes[val].size() == 0)
                indexes.erase(val);

            int num = nums.back();
            nums.pop_back();
            if(!(num == val && nums.size() == i)){

                nums[i] = num;
                indexes[num].erase(nums.size());
                indexes[num].insert(i);
            }

            return true;
        }
        return false;
    }

    /** Get a random element from the collection. */
    int getRandom() {
        int rndIndex = rand() % nums.size();
        return nums[rndIndex];
    }
};


int main() {

    return 0;
}