49. 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"]
]


利用map结构 
map详细说明参考： http://blog.csdn.net/shuzfan/article/details/53115922

class Solution {
public:
    vector<vector<string>> groupAnagrams(vector<string>& strs) {
        unordered_map<string, multiset<string>> mp;    
        for (string s : strs) {
            string t = s; 
            sort(t.begin(), t.end());    //对字串内的字符排序 便于比较
            mp[t].insert(s);             //t为s排序后的字串  ate eat 的排序后都是t = aet 是一样的 
        }
        vector<vector<string>> anagrams;
        for (auto m : mp) { 
            vector<string> anagram(m.second.begin(), m.second.end());    //second代表只抽取m的value部分 他们的key一样 anagram = [[eat] [ate] [eta]]
            anagrams.push_back(anagram);                                 
        }
        return anagrams;
    }
};