GroupAnagrams.java

package hashing;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;

/**
 * Created by gouthamvidyapradhan on 10/03/2017.
 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.
 */
public class GroupAnagrams
{
    private int[] A = new int[256];
    private HashMap<String, List<String>> hashMap = new HashMap<>();
    private List<List<String>> result = new ArrayList<>();
    /**
     * Main method
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception
    {
        String[] strs = {"huh", "tit"};

        List<List<String>> result = new GroupAnagrams().groupAnagrams(strs);
        for (List<String> l : result)
        {
            for(String s : l)
                System.out.println(s);
            System.out.println("-----");
        }
    }

    public List<List<String>> groupAnagrams(String[] strs)
    {
        for(int i = 0, l = strs.length; i < l; i ++)
        {
            Arrays.fill(A, 0);
            String s = strs[i];
            for(int j = 0, sl = s.length(); j < sl; j ++)
                A[s.charAt(j)]++;

            StringBuilder sb = new StringBuilder();
            for(int k = 0; k < 256; k ++)
            {
                if(A[k] != 0)
                    sb.append(k).append("").append(A[k]);
            }
            List<String> value = hashMap.get(sb.toString());
            if(value == null)
                value = new ArrayList<>();
            value.add(s);
            hashMap.put(sb.toString(), value);
        }

        for(String s : hashMap.keySet())
            result.add(hashMap.get(s));

        return result;
    }
}