leetcode[49]Anagrams

Given an array of strings, return all groups of strings that are anagrams.

Note: All inputs will be in lower-case.

class Solution {
public:
string tostring(string str)
{
    if(str.empty()||str.size()<=1)return str;
    string res=str;
    sort(res.begin(),res.end());
    return res;
}
vector<string> anagrams(vector<string> &strs) 
{
    vector<string> res0;
    res0.clear();
    if(strs.empty())return res0;
    map<string,vector<string>> strMap;
    strMap.clear();    
    string strTemp;
    for (vector<string>::iterator iter=strs.begin();iter!=strs.end();iter++)
    {
        strTemp=tostring(*iter);
        strMap[strTemp].push_back(*iter);
    }
    for(map<string,vector<string>>::iterator iter1=strMap.begin();iter1!=strMap.end();iter1++)
    {
        if(iter1->second.size()>1)
            res0.insert(res0.end(),iter1->second.begin(),iter1->second.end());
    }
    return res0;
}
};