Competitive/Collaborative Programming Class

/*
 *  Author: Son Pham
 *    Date: January 23, 2013
 * Purpose: Solves this problem using the simplest, but most inefficient approach.
 * Problem: 628 - Passwords
 */

import java.util.Arrays;
import java.util.Scanner;

public class Passwords {
    static String word;
    static int[] digits = new int[7];
    
    public static void main(String[] args) {
      
        int n,m;
        String[] words = new String[100];
        String[] rules = new String[1000];
        
        Scanner scan = new Scanner(System.in);
        while(scan.hasNext()){
            n = Integer.parseInt((scan.next()));
            for(int i = 0; i < n; i++){
                words[i] = scan.next();
            }
            m = Integer.parseInt((scan.next()));
            for(int i = 0; i < m; i++){
                rules[i] = scan.next();
            }
            System.out.println("--");
            for(int i = 0; i < m; i++){
                String rule = rules[i];
                Arrays.fill(digits,-1);
                int index = 0;
                int count = 0;
                while((index = rule.indexOf("0",index)) != -1){
                    digits[count++] = index++;
                }
                
                for(int j = 0; j < n; j++){
                    word = words[j];
                    char[] rChars = rule.toCharArray();
                    digits(rChars,0);
                }
            }
        }   
    }
    public static void digits(char[] ch, int d){
        int spot = d;
        for(int i = 0; i < 10; ++i){
            String op = "";
            ch[digits[spot]] = Character.forDigit(i,10);
            if(d < ch.length){
                if(digits[++d] != -1){
                    digits(ch,d);
                    ch[digits[d]] = Character.forDigit(0,10);
                    d = spot;
                    continue;
                }
            }
            for(char c : ch){
                op+=c;
            }
            op = op.replaceAll("#",word);
            System.out.println(op);
            
        }
    }
}

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