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:

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

编程珠玑上有介绍，先给每一个string置一个标识，这个标识用来后边的分类，因此用的是降序排列后的strig作为自身的标识。

再将具有相同标识的放在以前。

代码：

class Solution {

public:

    vector<vector<string>> groupAnagrams(vector<string>& strs) {

        map<string,vector<int>> m1;

         vector<vector<string>> result;

        for(int i=0;i<strs.size();++i)

        {

            string s1=strs[i];

            sort(s1.begin(),s1.end());

            m1[s1].push_back(i);

        }

        for(auto p:m1)

        {

            vector<string> v1;

            for(auto index:p.second)

            v1.push_back(strs[index]);

            sort(v1.begin(),v1.end());

            result.push_back(v1);

        }

        return  result;

    }

};