stack.cpp

数据结构与程序设计教材源码 数据结构与程序设计教材源码

 
Stack::Stack()
/*   
Pre:  None.
Post: The stack is initialized to be empty.
 */
{
   count = 0;
}
 
Error_code Stack::push(const Stack_entry &item)
/*   
Pre:  None.
Post: If the Stack is not full, item is added to the top
of the Stack.  If the Stack is full,
an Error_code of overflow is returned and
the Stack is left unchanged.
 */
{
   Error_code outcome = success;
   if (count >= maxstack)
      outcome = overflow;
   else
      entry[count++] = item;
   return outcome;
}
 
Error_code Stack::top(Stack_entry &item) const
/*   
Pre:  None.
Post: If the Stack is not empty, the top of
the Stack is returned in item.  If the Stack 
is empty an Error_code of underflow is returned.
 */
{
   Error_code outcome = success;
   if (count == 0)
      outcome = underflow;
   else
      item = entry[count - 1];
   return outcome;
}
 
bool Stack::empty() const
/*   
Pre:  None.
Post:
If the Stack is empty, true is returned.
Otherwise false is returned.
 */
{
   bool outcome = true;
   if (count > 0) outcome = false;
   return outcome;
}
 
Error_code Stack::pop()
/*   
Pre:  None.
Post: If the Stack is not empty, the top of
the Stack is removed.  If the Stack 
is empty, an Error_code of underflow is returned.
 */
{
   Error_code outcome = success;
   if (count == 0)
      outcome = underflow;
   else --count;
   return outcome;
}