Thread: Stack and Queues questions

I am preparing for a test and have answered some questions dealing with stacks and queues the teacher has provided as samples. Could someone check over my work?

Code:

// stack.h – complete header file for Stack ADT
#include <iostream>
using namespace std;

class StackFull { /* Empty Exception Class */ };
class StackEmpty { /* Empty Exception Class */ };
class Stack // An array implementation of Stack ADT for storing integers
{
private:
int* ptr; // Holds address of dynamically-allocated integer array
int top; // Array index of top-most integer on the stack
int size; // Maximum number of integers that may be stored in the stack

public:
Stack(int num); // Dynamically allocate 1-D array of integers of size num
                        // and configure empty stack
~Stack(); // Deallocates stack array
void Push(int n); // Add integer n to the top of the stack if not full
                          // Otherwise, throw StackFull exception
int Pop(); // Removes top integer from stack AND returns value to
               // client; throws StackEmpty exception if stack is empty
void MakeEmpty(); // Return stack to empty but usable state
bool IsFull() const; // Return true if stack is full; otherwise return false
bool IsEmpty() const; // Return true if stack is empty; otherwise return false
int Capacity() const; // Returns the maximum number of integers that may be
                                // stored in Stack object
}; // End Class Stack

1) Implement Stack.

Code:

Stack::Stack(int num)
{
 ptr=new int[num];
 top=0;
 size=num;
}

2) Implement Push method

Code:

void Stack::Push(int n)
{
 if(IsEmpty() )
   throw StackFull();
 else
 {
  ptr[top]=n;
  top++;
 }
}

3) Implement IsEmpty

Code:

bool Stack::IsEmpty() const
{
 return (top == 0);
}

4) Implement Pop

Code:

int Stack::Pop()
{
 if (IsEmpty())
   throw StackEmpty();
 else
 {
  int temp=ptr[top];
  top--;
  return temp;
 }
}

5) Implement Desctructor

Code:

Stack::~Stack()
{
 MakeEmpty();
}

6) Implement Capacity

Code:

int Stack::Capacity() const
{
 return size;
}

7) Implement IsFull

Code:

bool Stack::IsFull() const
{
 return (top == size);
}

The header code was provided and the questions 1-7 were multiple choice questions I had to answer. I am not writing specific code, just using the header to write a few functions. Just wanted to check and see if I got each one right.

Originally Posted by kmdv

Oh, so these points were actually questions.
You still have a bug in one of your method - the Pop() method.

Correct. Just had to chose between four sample codes provided or None of the above, because it is a multiple choice question. Are the others correct except Pop?

Implement Pop

Code:

int Stack::Pop()
{
 if (IsEmpty())
   throw StackEmpty();
 else
 {
  return ptr[top];
  top--;
 }
}

int Stack::Pop()

O_o

You have no idea how much seeing that upsets me.

Anyway, anon wasn't teasing you. You have a big bug and it isn't localized to any one function.

Put the code into a testbed and see what happens.

Soma

Originally Posted by phantomotap

O_o

You have no idea how much seeing that upsets me.

Anyway, anon wasn't teasing you. You have a big bug and it isn't localized to any one function.

Put the code into a testbed and see what happens.

Soma

Read the other posts. This is not code I am testing. Those 1-7 were questions are dealing with the header file up top.

why does seeing that upset you?

Let me just say that in real life C++ stack implementations such a signature causes a problem.

Read the other posts. This is not code I am testing.

I'm well aware. If you threw the code at a testbed you would know that those options are the wrong ones and have an idea about what the right ones would look like.

Soma

Originally Posted by anon

@phantomtap: It is unclear whether such a signature causes a problem here.

@OP: Which part is your answer? There appear to be bugs in both Push and Pop. These are your code?

Not my code, for each question there are 4 code options to choose from and also 'none of the above'. So for those, pop and push, I have chose the incorrect one. When I get back I will try to chose the correct one and post it. Most choices are very similar with just 1-2 lines different.

Originally Posted by anon

@phantomtap: It is unclear whether such a signature causes a problem here.

@OP: Which part is your answer? There appear to be bugs in both Push and Pop. These are your code?

Here is my correction for Push and Pop.

Implement Push

Code:

void Stack::Push(int n)
 if (IsFull())
  throw StackFull();
 else
 {
  top++;
  ptr[top]=n;
 }
}

Implement Pop

Code:

int Stack::Pop()
{
 if (IsEmpty())
  throw StackEmpty();
 else
 {
  top--;
  return ptr[top];
 }
}