Anagrams

Given an array of strings, return all groups of strings that are anagrams.

Note: All inputs will be in lower-case.

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思路：Every anagrams have the same sorted character arrays. So, we  create a hashmap to storage and the key is sorted character array and the value is anagrams list.
At last, we use iterator to add list to the result.
易错点： 添加进 map 时候， 注意 list 是否已经创建。 还有 最后 如果有anagram  list.size() > 1 才能添加入结果。

public class Solution {    public List<String> anagrams(String[] strs) {        List<String> ret = new ArrayList<String>();        if(strs.length < 1)            return ret;        HashMap<String, List<String>> map = new HashMap<String, List<String>>();        for(String s : strs){            char[] arr = s.toCharArray();            Arrays.sort(arr);            String key = new String(arr);            if(map.containsKey(key)){                List<String> list = map.get(key);                list.add(s);            }else{                List<String> list = new ArrayList<String>();                list.add(s);                map.put(key, list);            }        }        Iterator<String> it = map.keySet().iterator();        while(it.hasNext()){            List<String> list = map.get(it.next());            if(list.size() > 1)                ret.addAll(list);        }        return ret;    }}