Task:

 Generate a string with   N   opening brackets   [   and with   N   closing brackets   ],   in some arbitrary order. 
 Determine whether the generated string is balanced; that is, whether it consists entirely of pairs of opening/closing brackets (in that order), none of which mis-nest.


Examples

   (empty)      OK
   []           OK   
   [][]         OK   
   [[][]]       OK 
   ][         NOT OK
   ][][       NOT OK
   []][[]     NOT OK



isBalanced = function(str) 
	level = 0
	for c in str
		if c == "[" then level = level + 1
		if c == "]" then level = level - 1
		if level < 0 then return false
	end for
	return level == 0
end function