leetcode49 Group Anagrams

Given an array of strings, group anagrams together.

For example, given: ["eat", "tea", "tan", "ate", "nat", "bat"], 
Return:

[
  ["ate", "eat","tea"],
  ["nat","tan"],
  ["bat"]
]

Note:

1. For the return value, each inner list's elements must follow the lexicographic order.
2. All inputs will be in lower-case.

   class Solution {
   public:
       vector<vector<string> > groupAnagrams(vector<string>& strs) {
           sort(strs.begin(),strs.end());
           vector<vector<string> > ans;
           map<string,int> tmap;//string为单个字符串排序后的字符串，int为该类string的list在ans中下表位置
           map<string,int>::iterator iter;
           int size=strs.size();
           for(int i=0;i<size;i++)
           {
               string temp=strs[i];
               sort(temp.begin(),temp.end());
               iter=tmap.find(temp);
               if(iter==tmap.end())
               {
                   vector<string> tv;
                   tv.push_back(strs[i]);
                   ans.push_back(tv);
                   tmap[temp]=ans.size()-1;
               }
               else
               {
                   int p=iter->second;
                   ans[p].push_back(strs[i]);
               }
           }
           return ans;
       }
   };