Combinations of Brackets

Develop an algorithm to find out all valid combinations of n brackets. Like for n =3 possible combinations can be ((())) or ()()() or (()()) and so on.
Answer:

Use a stack. 
while( not end of input )
{
  ch = input character
  if ( ch is '(' ) then push it to stack.
  else pop from stack., and if the poped item is not '(' then error.
}
The stack should be empty now.