(UVA) Knuth's Permutation - Solution

Link to the problem: https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=646&page=show_problem&problem=1004

The solution below used Backtracking to solve this problem.


import java.io.*;
import java.util.*;

class Main {
    public String sequence;
    BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
  
    public void rec(int index, char[] array) throws NumberFormatException, IOException {
        if (index == sequence.length()) {
            for (int i = 0; i < array.length; i++) {
                bw.write(array[i]);
            }
            bw.write("\n");
            return;
        }
      
        for (int j = index; j > 0; j--) {
            array[j] = array[j-1];
        }
        array[0] = sequence.charAt(index);
        rec(index+1, array);
        for (int i = 1; i <= index; i++) {
            char tmp = array[i];
            array[i] = array[i-1];
            array[i-1] = tmp;     
            rec(index+1, array);
        }
    }
  
    public void process() throws NumberFormatException, IOException {
        Scanner sc = new Scanner(System.in);

        int numCase = 0;
        while (sc.hasNext()) {
            if (numCase > 0) {
                bw.write("\n");
            }
            sequence = sc.next();
          
            char[] array = new char[sequence.length()];
            rec(0, array);
          
            numCase++;
        } 
                                             
        bw.flush();
        bw.close();
      
        return;
    }
  
    public static void main(String[] args) throws NumberFormatException, IOException {
        Main m = new Main();
        m.process();
      
        System.exit(0);
    }
}