LeetCode 49. Group Anagrams

原题链接在这里：https://leetcode.com/problems/anagrams/

题目：

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.

题解：

用sort的方式找出anagram的base型，用来当HashMap的key.

Time Complexity: O(nlogn * strs.length), n是strs中最长string的长度. Space: O(hm.size()), HashMap size.

AC Java:

 1 class Solution {
 2     public List<List<String>> groupAnagrams(String[] strs) {
 3         HashMap<String, List<String>> hm = new HashMap<>();
 4         for(String s : strs){
 5             char [] sArr = s.toCharArray();
 6             Arrays.sort(sArr);
 7             String sortedStr = new String(sArr);
 8             
 9             hm.putIfAbsent(sortedStr, new ArrayList<>());
10             hm.get(sortedStr).add(s);
11         }
12         
13         return new ArrayList<List<String>>(hm.values());
14     }
15 }

类似Group Shifted Strings.