gistfile1.java

      String exp = "(x+(xx)+((xxx)+))+";
      int close=-1, open=-1;
      boolean check = true, hasCandidate = false;
      int counter = 0;
      
      for(int nextStart = exp.length()-1; nextStart!=0; ){
         check = true; hasCandidate = false; counter = 0;
         close = open = -1;
         for(int i = nextStart; i>=0; i--){ // for every special character
            if(exp.charAt(i)=='+' && i-1>=0 && exp.charAt(i-1)==')' && check){ // if firste checked specChar preceed by )
               check = false;
               nextStart=i-1; // shift next pass
               close = i + 1; // set closing position
               if(i+1<exp.length() && exp.charAt(i+1)==')'){ // if ) follows it can be already bracketed
                  hasCandidate = true; // its only candidate
               }
            } else if(!check){ // ok count closing and opening brackets
               if(exp.charAt(i)==')')
                  counter++;
               if(exp.charAt(i)=='(')
                  counter--;
               if(counter==0){ // its zero, we should place bracket here
                  if(hasCandidate){ // if this is candidate check if it has closing bracket if yes, forget it
                     if((i-1>=0)&&exp.charAt(i-1)=='(')
                        break;
                  }
                  open = i;
                  break;
               }
            }
            if(i==0 && check){ // if we processed all the specchars and our index is 0, just break;
               nextStart=0;
            }
         }
         if(open >= 0 && close>= 0){ // process only non negative intervals
            System.out.println(String.format("%d %d", open, close));
            StringBuffer sb = new StringBuffer(exp);
            sb.insert(close, ']');
            sb.insert(open, '[');
            exp = sb.toString();
         }
      }