StringPerm

package StringPerm;

import java.util.ArrayList;

/*
 * Name: George Colon
 * Date: 11/20/2017
 * Course Number: CSC 111
 * Course Name: Data structures
 * Email: Gcolon6085@student.stcc.edu
 */

import java.util.Scanner;

public class StringPermHomeWork {


    //**********************************************

    private static void process(Scanner sc, String args[]) {
        // Code here is merely a sample
        String x;
        System.out.print("Please enter a string: ");
        x = sc.next();
        sc.nextLine();  // IMPORTANT!! Reset Scanner
        System.out.println("Processing " + x + " ...");
        displayPermutation(x);

    }

    //**********************************************

    private static boolean doThisAgain(Scanner sc, String prompt) {
        System.out.print(prompt);
        String doOver = sc.nextLine();
        return doOver.equalsIgnoreCase("Y");
    }

    //**********************************************

    public static void main(String args[]) {
        final String TITLE = "CSC111 String Permutation";
        final String CONTINUE_PROMPT = "Do this again? [y/N] ";

        System.out.println("Welcome to " + TITLE);
        Scanner sc = new Scanner(System.in);
        do {
            process(sc, args);
        } while (doThisAgain(sc, CONTINUE_PROMPT));
        sc.close();
        System.out.println("Thank you for using " + TITLE);
    }

    public static void displayPermutation(String s) {
        // using this array list to keep track of already printed outputs.
        // If the char has matching characters this e.g. aaabbc without it we will get
        // outputs multiple times
        // The math of this is 6! / 3!*2! this will give 60 outputs yet without the
        // array list we would have 720.
        ArrayList<String> used = new ArrayList<String>();
        worker("", s, used);

    }

    public static void worker(String s1, String s2, ArrayList<String> used) {

        if (s2.length() == 0 && used.contains(s1) == false) {
            used.add(s1);
            System.out.println(s1);
        } else {

            StringBuilder string = new StringBuilder(s2);
            StringBuilder hold = new StringBuilder(s1);
            for (int i = 0; i < string.length(); i++) {
                char h = string.charAt(i);
                // Move down a level -Recursively solve-
                worker(hold.append(h).toString(), string.deleteCharAt(i).toString(), used);
                // add the removed back in the order they were removed
                string.insert(i, h);
                hold.deleteCharAt(hold.length() - 1);
            }
        }
    }

}