Crypto-equivalence

CE.java

import java.util.*;
class CE{
    public static void main(String[] args){
        String[] test = {"car", "mom", "dad", "book", "ant", "bob"};
        ArrayList<ArrayList<String>> t = ce(test);
    }


    //This basically transforms each character in temporary cipher that's based on the unique characters found
    //within the string you are currently processing. Based off of that information, we are able to keep track of similar
    //formations of 1-to-1 mappings of various strings.

    static ArrayList<ArrayList<String>> ce(String[] arr){
        HashMap<String, ArrayList<String>> map = new HashMap<String, ArrayList<String>>();

        for(String s : arr){
            HashMap<Character, Character> cipher = new HashMap<Character, Character>();

            //This will map from every unique character found in ascending order.
            char lastUnique = 'a';

            StringBuilder sb = new StringBuilder();

            for(Character c : s.toCharArray()){
                if(!cipher.containsKey(c)){
                    cipher.put(c, lastUnique);
                    //move the last unique character forward
                    lastUnique++;
                }
                sb.append(cipher.get(c));
            }

            String key = sb.toString();
            if(map.containsKey(key)){
                ArrayList<String> list = map.get(key);
                list.add(s);
                map.put(key, list);
            }
            else{
                ArrayList<String> list = new ArrayList<String>();
                list.add(s);
                map.put(key, list);
            }
        }

        ArrayList<ArrayList<String>> listOfLists = new ArrayList<ArrayList<String>>();
        //iterate through the map.
        for(String key : map.keySet()){
            ArrayList<String> list = new ArrayList<String>();
            list.addAll(map.get(key));
            listOfLists.add(list);
        }

        System.out.println(listOfLists);
        return listOfLists;

    }
}

For example, "mom" is temporarily stored as "aba". This is put into the HashMap. Later on, we come across "dad", which is also temporarily stored as "aba", we simply update the list within that key in the HashMap.