Array Index Out of Bound

[ankiit]

Hi,

Please help me with the below one:-

class Stack
{
	int stck[] = new int[10];
	int tos;

/*Constructor*/

Stack()
	{
	tos = 0;
	}

/*push routine to enter data into the LIFO(stack) structure,*/

void push(int item)
	{
		if(tos > 9)
		{
			System.out.println("Stack is Full");
		}
		
		else
			stck[tos++] = item;

	}

/*pop routine to pull values back from stack*/

int pop()
	{
		if(tos < 0)
		{
			System.out.println("Stack is already empty");
			return 0;
		}

		else
			return stck[tos--];
	 }

}


class StackDemo
{
	public static void main(String[] args)
	{
		Stack s1 = new Stack();
		Stack s2 = new Stack();

	/*pushing integers onto stack*/
		for(int i = 0; i<=9; i++)
			s1.push(i);
		for(int j = 10; j<=19; j++)
			s2.push(j);
//pop integers from stack
	for(int i = 0; i<=9; i++)
			System.out.println(s1.pop());
			System.out.println();
		for(int j = 10; j<=19; j++)
			System.out.println(s2.pop());
	
	}
	

}

[Fubarable]

If you have an error, it's usually wise to show us the actual error message, and also indicate with a comment which line causes the error.

[JosAH]

b.t.w. there are four different stacks: ascending and descending stacks and stacks where the stack pointer refers to the first free element or to the most recently pushed element. Your push and pop methods implement different stack strategies.

kind regards,

Jos

[ankiit]

Hi Fubarable,

Apologies for the inconvenience.

I have attached the screen shot of the error with my post.

Thanks
Ankit.

[ankiit]

Hi All,

I have figured out the issue with my code, I found that instead of the following I should use:-

int pop()                      //causes error
    {
        if(tos < 0)
        {
            System.out.println("Stack is already empty");
            return 0;
        }
 
        else
            return stck[tos--];

int pop()                                            //to be used
    {
        if(tos < 0)
        {
            System.out.println("Stack is already empty");
            return 0;
        }
 
        else
            return stck[--tos];

This solved my problem, actually I was of the view that the final value for tos is 9 which caused the problem, but since the final value is 10 , i corrected my code to work fine.

But now I want to initialize tos to the upper limit of the stack i.e 9, looking forward for your esteemed help in the matter.

Thanks
Ankit

[JosAH]

But now I want to initialize tos to the upper limit of the stack i.e 9, looking forward for your esteemed help in the matter.

Reread my reply #3 again ...

kind regards,

Jos

[ankiit]

Hi Jos,

Thanks a lot for the information.

Please share in which of the 4 categories my push and pop routine falls.

Request you to please provide a brief reference to 4 different strategies of implementing stacks.

Thanks in Advance
Best Regards,
Ankit

[JosAH]

Please share in which of the 4 categories my push and pop routine falls.

Request you to please provide a brief reference to 4 different strategies of implementing stacks.

You stack is an ascending stack (in your original example) because the elements are pushed from low to high, but your push operation assumed an empty stack (the stack pointer refers to the first available slot), while your pop operation assumes a full stack (the stack pointer refers to the last pushed element). Both operations should assume either an empty stack or a full stack, i.e. for an empty, ascending stack:

push: stack[top++]= element;
pop: return stack[--top];

A full stack uses the following operations:

push: stack[++top]= element;
pop: return stack[top--];

Note that I left out the stack full/empty tests.

kind regards,

Jos

[ankiit]

Hi Jos,

Thanks a lot for the information.

I have understood and implemented both ascending and descending stacks, thanks to you :).

But still I am unable to understand 2 of the following stacks:- "pointer points to first free element or to the most recently pushed element"

Seeking your help in this regard.
Thanks
Ankit

[ankiit]

Hi Jos,

For implementing the descending stack i have used the following code:-

class Stack
{
    int stck[] = new int[10];
    int tos;
 
/*Constructor*/
 
Stack()
    {
    tos = 9;
    }
 
/*push routine to enter data into the LIFO(stack) structure,*/
 
void push(int item)
    {
        if(tos < 0)
        {
            System.out.println("Stack is Full");
        }
         
        else
            stck[tos--] = item;
 
    }
 
/*pop routine to pull values back from stack*/
 
int pop()
    {
        if(tos > 9)
        {
            System.out.println("Stack is already empty");
            return 0;
        }
 
        else
            return stck[++tos];
     }
 
}
 
 
class StackImpl
{
    public static void main(String[] args)
    {
        Stack s1 = new Stack();
        Stack s2 = new Stack();
 
    /*pushing integers onto stack*/
        for(int i = 0; i<=9; i++)
            s1.push(i);
        for(int j = 10; j<=19; j++)
            s2.push(j);
//pop integers from stack
    for(int k = 0; k<=9; k++)
            System.out.println(s1.pop());
            System.out.println("empty line");

        for(int l = 10; l<=19; l++)
            System.out.println(s2.pop());
     
    }
     
}

I think it just gave me the correct output but it ruined the stack concept.

Please also find the output



Please give your valuable suggestions.

Thanks in advance

Best Regards,
Ankit