50. 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.

Solution

(1) Java

class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        Map<String, List<String>> map = new HashMap<>();
        for (String str : strs) {
            int[] chars = new int[26];
            char[] sc = str.toCharArray();
            for (char c : sc) {
                chars[c-'a']++;
            }
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < 26; i++) {
                if (chars[i] != 0) {
                    sb.append('a'+i).append(chars[i]);
                }
            }
            String key = sb.toString();
            if (!map.containsKey(key)) {
                map.put(key, new ArrayList<String>());
            }
            map.get(key).add(str);
        }
        List<List<String>> rst = new ArrayList<>();
        for (List<String> list : map.values()) {
            rst.add(list);
        }
        return rst;
    }
}

(2) Python

class Solution:
    def groupAnagrams(self, strs):
        """
        :type strs: List[str]
        :rtype: List[List[str]]
        """
        cache = {}
        for word in strs:
            words = ''.join(sorted(word))
            if cache.get(words) == None:
                cache[words] = []
            cache[words].append(word)
        rst = []
        for l in cache.values():
            rst.append(l)
        return rst

(3) Scala