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.

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;
    }
};