Thread: Bracket Checker

Originally Posted by Sebastiani

So basically, when you encounter an 'opening' symbol, simply push the corresponding 'closing' symbol onto the stack. If you come across a 'closing' symbol, just check the stack. If it isn't what you expected, then there is an error, otherwise, discard the current symbol (pop the stack) and proceed. If there is an attempt to pop an empty stack, or the stack is not empty when you are done, then it is ill-formed.

I am really very sorry. I dint get what you are trying to say =((!!
When we encounter an opening symbol why we push the corresponding closing symbol??

Originally Posted by Fatima Rizwan

I am really very sorry. I dint get what you are trying to say =((!!
When we encounter an opening symbol why we push the corresponding closing symbol??

It's just a convention - you can do it either way, really. Whatever seems most logical to you.

Code:

while ( input != 13 )
      {
       if input is '(' or '{' or '[' or ')' or '}' or ']' 
          {
          if input is '(' or '{' or '['
              push it into the stack.
          else if input is  ')' or '}' or ']' 
              {
              if stack is empty
                       report error.
              pop cell from stack
              if cell "matches input" 
                       we are ok.
              else if cell dont "matches input" or stack is empty 
                       report error.
              }
          }
      }
   if  the stack is not empty
        report error.

How about this??

Very good.

A couple of possible issues to be aware of, though:
1) The stopping condition should be on the null-terminator (0, the end of the string), not a newline (13).
2) The condition 'if cell "matches input"' would be incorrect, considering that if the input, for instance, is a closing bracket, then the cell should be an opening bracket. This is actually why it was suggested to push the 'closing' symbol, as it would make the checking logic a little simpler.
3) It's probably necessary to implement an 'is_empty' member function, or similar.

Everything else looks pretty close to being correct. Try to implement it in code now, and see what you come up with.