private static void decode(String s) { int len=s.length(); StringBuffer sb=new StringBuffer(); ArrayList<Integer> al=new ArrayList<Integer>(); for(int i=0;i<len;){ if(isNum(s.charAt(i))) { int  end=i+1; int j=i+1; while(j<len) { if(isNum(s.charAt(j))) { end=j+1; j++; } else break; } if(al.size()==0) { for(int z=0;z<Integer.valueOf(s.substring(i,end))-1;z++) { sb.append(s.substring(0,i)); } al.add(end); } else{ for(int z=0;z<Integer.valueOf(s.substring(i,end))-1;z++) { sb.append(s.substring(al.get(0),i)); } al.set(0, end); } i=end; } else { sb.append(s.charAt(i)); i++; } } System.out.println(sb.toString()); } private static boolean isNum(char c) { if(c-48>=0 && c-48<=9) { return true; } return false; }