leetcode:字母异位词分组

class Solution {
public:
    map<string,vector<string>> m;
    vector<vector<string>> groupAnagrams(vector<string>& strs) 
    {
        vector<vector<string>> ret;
        for(auto& s:strs)
        {
            auto tmp = s;
            sort(tmp.begin(),tmp.end());
            m[tmp].push_back(s);
        }
        for(auto& it:m)
        {
            ret.push_back(it.second);
        }
        return ret;
    }   
};