Leetcode: Anagrams

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

Note: All inputs will be in lower-case.

We can sort each string and store it in a hashmap to identify when a string has an anagram. The algorithm runs inO(n k log k). 

Code from http://www.darrensunny.me/leetcode-anagrams/
public ArrayList<String> anagrams(String[] strs) {
    ArrayList<String> res = new ArrayList<String>();
    if(strs == null || strs.length == 0)
        return res;
    HashMap<String, ArrayList<String>> map = new HashMap<String, ArrayList<String>>();
    for(int i=0;i<strs.length;i++)
    {
        char[] charArr = strs[i].toCharArray();
        Arrays.sort(charArr);
        String str = new String(charArr);
        if(map.containsKey(str))
        {
            map.get(str).add(strs[i]);
        }
        else
        {
            ArrayList<String> list = new ArrayList<String>();
            list.add(strs[i]);
            map.put(str,list);
        }
    }
    Iterator iter = map.values().iterator();
    while(iter.hasNext())
    {
        ArrayList<String> item = (ArrayList<String>)iter.next();
        if(item.size()>1)
            res.addAll(item);
    }
    return res;
}
Read full article from My Own Notes: Leetcode: Anagrams