leetcode——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"]
]

Note:

1. For the return value, each inner list's elements must follow the lexicographic order.
2. All inputs will be in lower-case.

class Solution {
public:
    vector<vector<string>> groupAnagrams(vector<string>& strs) {
        if (strs.empty())
            return vector<vector<string> >();

        int len = strs.size();

        //将字符串数组按照字典顺序排序
        sort(strs.begin(), strs.end());

        //存储结果
        vector<vector<string> > ret;

        //利用哈希思想构建map，将排序后相等的字符串存在相应的vector
        map<string, vector<string>> mv;

        for (int i = 0; i < len; i++)
        {
            string str = strs[i];
            sort(str.begin(), str.end());

            mv[str].push_back(strs[i]);
        }

        for (map<string, vector<string> >::iterator iter = mv.begin(); iter != mv.end(); iter++)
            ret.push_back(iter->second);

        return ret;

    }
};