Leetcode 49. Group Anagrams

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: All inputs will be in lower-case.

题目链接：https://leetcode.com/problems/group-anagrams/description/

题目大意：给定一些字符串，把由相同字母组成的字符串归为一组，放到新的二维字符串数组中，每一行是同一组字符串。

解题思路：用到了map数据结构，键key是按字典序排列的字符串，值是与key有相同字母组合的字符串的vector数组。遍历字符串数组，获取每个字符串的按字典序升序排列的key，放入key对应的map数组中。再遍历一次字符串数组，把对应key的map数组压入结果数组ans中。

代码：

class Solution {
public:
    vector<vector<string> > groupAnagrams(vector<string>& strs) {
        vector<vector<string> > ans;
        int n = strs.size();
        map<string,vector<string> > mp;  
        map<string,int> vis;      
        for(int i = 0;i < n; i ++){
            string s = strs[i];
            sort(s.begin(),s.end());
            vis[s] = 1;
            mp[s].push_back(strs[i]);
        }
        for(int i = 0;i < n;i ++){
            string s = strs[i];
            sort(s.begin(),s.end());
            if(vis[s]){
                ans.push_back(mp[s]);
                vis[s] = 0;
            }
        }
        return ans;
    }
};