Poj Solution 1302

http://poj.org/problem?id=1302

/* @author:zeropinzuo */
import java.io.*;
import java.util.*;

public class Main{
 static Scanner cin;
 public static void main(String args[]){
   cin = new Scanner(System.in);
   while(run()==true)
        ;
 }

static boolean run(){
  String marker = cin.next();
  if(marker.compareTo("ENDOFINPUT")==0)
    return false;

  int n = cin.nextInt();
  Sequence seq = new Sequence(cin.next());
  System.out.println(seq.mutatedSequence());
  cin.next();
  return true;
 }

}

class Sequence{
 char[] content;
 public Sequence(String s){
   content = s.toCharArray();
 }

 public Sequence(char[] content){
   this.content = content;
 }

 private int mutate(int start){
  int count;

  if(start>=content.length)
   return 0;
  char c = content[start];
  if(isLetter(c)){
    count = mutate(start+1);
    content[start] = (char)(count%10+'0');
    count++;
    return count;
   }
  else if(c == '0')
    return 0;
  else if(isNumber(c)){
    content[start] = (char)(c-1);
    if((start+c-'0')< content.length)
    count = mutate(start+c-'0');
    else
    count = mutate(start+1);
    count++;
    return count;
  }
            
  return -1;
}

 private boolean isLetter(char c){
   if((c<='Z')&&(c>='A'))
     return true;
   return false;
  }

 private boolean isNumber(char c){
   if((c<='9')&&(c>='0'))
     return true;
   return false;
 }


 String mutatedSequence(){
   mutate(0);
   return new String(content);
 }
}