Use a hash table to record it. The tricky part is that when the hash value is > 0, it is the index + 1. Otherwise, that string already exists in result list.

 

1 class Solution { 2 public: 3     vector
     
       anagrams(vector
      
        &strs) { 4         vector
       
         result; 5         int len = strs.size(); 6         if (len < 2) return result; 7         unordered_map
        
          mapping; 8         for (int i = 0; i < len; i++) { 9             string tmp = strs[i];10             sort(tmp.begin(), tmp.end());11             if (mapping[tmp]) {12                 if (mapping[tmp] > 0) {13                     result.push_back(strs[mapping[tmp]-1]);14                     mapping[tmp] = -1;15                 }16                 result.push_back(strs[i]);17             } else {18                 mapping[tmp] = i+1;19             }20         }21         return result;22     }23 };