49. Group Anagrams

49. Group Anagrams
    Given an array of strings, group anagrams together.

Example:

Input: [“eat”, “tea”, “tan”, “ate”, “nat”, “bat”],
Output:
[
[“ate”,“eat”,“tea”],
[“nat”,“tan”],
[“bat”]
]
Note:

All inputs will be in lowercase.
The order of your output does not matter.
python

class Solution:
    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
      
        words = {}
        res = []
        for word in strs:
            sortedword = str(sorted(word))
            if sortedword in words:
                res[words[sortedword]].append(word)
            else:
                res.append([word])
                words[sortedword] = len(res) - 1 
        return res

tips:
word list的key值是字符串，值是res第几个数组
java：

class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        List<List<String>>  res = new ArrayList<List<String>>();
        Map<String,Integer> mp = new HashMap<String,Integer>();
        for(String str : strs){
            char[] ch = str.toCharArray();
            Arrays.sort(ch);
            String s = new String(ch);
            if(mp.containsKey(s)){
                List li = res.get(mp.get(s));
                li.add(str);
            }
            else{
                List li = new ArrayList();
                li.add(str);
                res.add(li);
                mp.put(s,res.size()-1);
            }
        }
        return res;
        
    }
}

tips:
先将字符串转换成字符数组吗，再将数组进行排序，接着在判断是否在map的key值中，在的话将字符串放入相应的List中，不在的话重新初始化一个列表，并将字符串放入。