我的教授“实现静态抽象数据类型”是什么意思？

Question

In my class for our assignment we are making two different Abstract Data Types, Double Stack and Leaky Stack . I have no problem creating these, but my professor put in the assignment details for both of these ADTs to "Give an efficient static implementation of the ADT". But what the hell does that mean? I could ask him tomorrow, but I want to get this assignment done today. Anyone have any idea what he means by this?

Answer 1

One possible interpretation is that the solutions are to use a fixed size "static" underlying structure (such as an array), rather than using a dynamic growing amount. Each stack, therefore, would have a pre-assigned maximum capacity. Therefore, I would expect an exception to be thrown on a push(...) operation that would exceed the capacity of the stack (just as a pop() operation would throw on an empty stack).

An example of a static implementation (though it allows setting the total capacity), might be like the following. Here the access will always be O(1) as an index is directly used, there is no traversal of the data structure, and no memory re-allocation. Note the code is example, and has not been tested. The use of the Generic could be removed if the approach in question specifies the specific type of stack (such as int or char).

public class AnotherStack<T>
{
  private final T[] values;
  private int loc = 0;

  // must use the suppress, as we are using a raw Object array
  //   which is necessitated as cannot make a generic array  
  // See Effective Java
  @SuppressWarnings("unchecked")
  public AnotherStack(int size)
  {
    values = (T[])new Object[size];
  }


  public void push(T val)
  {
      if (loc < values.length) {
          values[loc++] = val;
      }
      else {
          throw new IllegalStateException("Stack full");
      }
  }

  public T pop()
  {
      if (loc == 0) {
          throw new IllegalStateException("Stack empty");
      }
      return (values[--loc]);
  }

  // other methods
}