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:
    vector<string> anagrams(vector<string> &strs) 
    {
        vector<string> result;
        map<string,int> mapindex;
        for(int i=0;i<strs.size();i++)
        {
            string str=strs[i];
            sort(str.begin(),str.end());
            if(mapindex.find(str)==mapindex.end())
                mapindex[str]=i;
            else
            {
                if(mapindex[str]>-1)
                {
                    result.push_back(strs[mapindex[str]]);
                    mapindex[str]=-1;
                }
                result.push_back(strs[i]);
            }
        }
        return result;
    }
};