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class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k) {
       map<int, int> mNums;
       mNums.clear();
       for (int i = 0;i < nums.size();i++)
       {
           map<int,int>::iterator it = mNums.find(nums[i]); 
           if (mNums.end() == it)
           {
               mNums.insert(pair<int,int>(nums[i], i));
           }
           else
           {
               if (i - it->second <= k)
               {
                   return true;
               }
               mNums.erase(it);
               mNums.insert(pair<int,int>(nums[i], i));
           }
       }
       return false;
    }
};