【Leetcode】Group Anagrams

题目链接：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:

1. For the return value, each inner list's elements must follow the lexicographic order.
2. All inputs will be in lower-case.

思路：

将每个字符串的字符排序，将排序后的相同字符串保存在map中，最后要对结果字典序排序。

算法：

	public List<List<String>> groupAnagrams(String[] strs) {
		List<List<String>> strss = new ArrayList<List<String>>();
		HashMap<String, List<String>> maps = new HashMap<String, List<String>>();
		for (String s : strs) { // 字符串内排序，并保存对应关系
			char c[] = s.toCharArray();
			Arrays.sort(c);
			if (!maps.containsKey(String.valueOf(c))) {
				List<String> l = new ArrayList<String>();
				l.add(s);
				maps.put(String.valueOf(c), l);
			} else {
				List<String> l = maps.get(String.valueOf(c));
				l.add(s);
				maps.put(String.valueOf(c), l);
			}
		}
		Iterator<String> set = maps.keySet().iterator();
		while (set.hasNext()) {
			List<String> l = maps.get(set.next());
			Collections.sort(l); // 因为要求list内部字符串要字典序，所以对list进行排序，可以用collections对list排序
			strss.add(l);
		}
		return strss;
	}