K Empty Slots_2.cpp

class Solution {
public:
   int kEmptySlots(vector<int>& flowers, int k) {
       int len = flowers.size();
       set<int> bloom;
       for(int i = 0; i < len; ++i)
       {
           int pos = flowers[i];
           auto iter = bloom.insert(pos).first;
           if(iter != bloom.begin())
           {
               --iter;
               if(pos - *iter == k + 1)return i + 1;
               ++iter;
           }
           ++iter;
           if(iter != bloom.end() && *iter - pos == k + 1)
               return i + 1;
       }
       return -1;
   }
};