Anagrams

-----QUESTION-----

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

Note: All inputs will be in lower-case.

-----SOLUTION-----

class Solution {public:    vector<string> anagrams(vector<string> &strs) {        vector<string> res;        if (strs.size() <= 1) return res;        map<string,int> anagram;        for (int i = 0; i < strs.size(); ++i)        {            string s = strs[i];            sort(s.begin(), s.end());            if (anagram.find(s) == anagram.end()) {                anagram.insert(make_pair(s, i));            } else {                if (anagram[s] >= 0) {                    res.push_back(strs[anagram[s]]);                    anagram[s] = -1;                }                res.push_back(strs[i]);            }        }        return res;    }};