class Solution {
public:
    int singleNumber(vector<int>& nums) {
        if(nums.empty())
            return 0;
        unordered_map<int,int> mp;
        for(int i : nums)
        {
            mp[i]+=1;
        }
        int k =0;
        for(int i : nums)
        {
            std::cout<<mp[i]<<", ";
            if(mp[i]<2)
            {
                k = i;
            }
        }
        return k;

    }
};