class Solution {

public:

    bool containsNearbyDuplicate(vector<int>& nums, int k) {

          map<int,char> exit_last;

          for(int i=0;i<nums.size();i++){

            if(exit_last.find(nums[i]) == exit_last.end()){

                 exit_last.insert(pair<int,char>(nums[i],i));

            }

            else{

                 if(i - exit_last[nums[i]] <= k)

                       return true;

                 exit_last[nums[i]] = i;

            }

         }

         return false;

    }

};