49. Group 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.

链接：https://leetcode.com/problems/anagrams/#/description

4/19/2017

37ms, 37%

注意的问题：

1. 第7，8，9行的写法

2. 第19，20行写法

public class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        Map<String, List<String>> m = new HashMap<String, List<String>>();
        List<List<String>> ret = new ArrayList<>();
        for (int i = 0; i < strs.length; i++) {
            String s = strs[i];
            char[] ar = s.toCharArray();
            Arrays.sort(ar);
            String t = String.valueOf(ar);
            List<String> l;
            if (m.containsKey(t)) {
                l = m.get(t);
            } else {
                l = new ArrayList<String>();
            }
            l.add(s);
            m.put(t, l);
        }
        for (Map.Entry<String, List<String>> entry: m.entrySet()) {
            List<String> value = entry.getValue();
            ret.add(value);
        }
        return ret;
    }
}

更多讨论：https://discuss.leetcode.com/category/57/anagrams