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.

Solution:

public class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        List<List<String>> ans = new ArrayList<>();
        Map<String, List<String>> map = new HashMap<>();
        for(String s : strs){
            char[] chs = s.toCharArray();
            Arrays.sort(chs);
            String key = String.valueOf(chs);
            if(map.containsKey(key)){
                map.get(key).add(s);
            } else {
                List<String> l = new ArrayList<>();
                l.add(s);
                map.put(key, l);
            }
        }
        for(List<String> list : map.values()) ans.add(list);
        return ans;
    }
}