Group Anagram

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

from collections import defaultdict

class Solution(object):
    def groupAnagrams(self, strs):
        """
        :type strs: List[str]
        :rtype: List[List[str]]
        """
        mapper, result = defaultdict(list), []
        for s in strs:
            s_str = "".join(sorted(s))
            mapper[s_str].append(s)
        for a in mapper.values():
            a.sort()
            result.append(a)
        return result

public class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        if (strs == null || strs.length == 0) return new ArrayList<List<String>>();

        Map<String, List<String>> map = new HashMap<>();
        Arrays.sort(strs);

        for(String s : strs) {
            char [] c = s.toCharArray();
            Arrays.sort(c);
            String key = String.valueOf(c);
            if(!map.containsKey(key)) map.put(key, new ArrayList<>());
            map.get(key).add(s);
        }

        return new ArrayList<List<String>>(map.values());
    }
}