[LeetCode java solution] – String/Hashtable – Anagrams

Problem:

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

Note: All inputs will be in lower-case.

Method:

Create a HashMap:

key: String (after chars are sorted);

value: The specific corresponding string.

Then, iterate through the HashMap. If there is a key with more than two values, we add them into the result container.

Code:

public class Solution {
    public ArrayList<String> anagrams(String[] strs) {
        if (strs == null || strs.length == 0) return null;
        ArrayList<String> res = new ArrayList<String>();
        
        HashMap<String, ArrayList<String>> dict = new HashMap<String, ArrayList<String>>();
        
        for (int i = 0; i < strs.length; i++){
            char[] c = strs[i].toCharArray();
            Arrays.sort(c);
            String s = new String(c);
            if (dict.containsKey(s)){
                dict.get(s).add(strs[i]);
            }else{
                ArrayList<String> l = new ArrayList<String>();
                l.add(strs[i]);
                dict.put(s,l);
            }
        }
        Iterator iter = dict.values().iterator();
        while(iter.hasNext()){
            ArrayList<String> temp = (ArrayList<String>)iter.next();  //cast type!!
            if(temp.size() > 1){
              res.addAll(temp);
            }
        }
        return res;
    }
}