GATE CSE 2004 | Question: 3

Question

A single array $A[1 \ldots \text{MAXSIZE}]$ is used to implement two stacks. The two stacks grow from opposite ends of the array. Variables $top1$ and $top2$ $(top1 < top 2)$ point to the location of the topmost element in each of the stacks. If the space is to be used efficiently, the condition for $\text{“}\textsf{stack full}\text{”}$ is

• A. $(top1 = \text{MAXSIZE} / 2)$ and $(top2 = \text{MAXSIZE} / 2 + 1)$

• B. $top1 + top2 = \text{MAXSIZE}$

• C. $(top1 = \text{MAXSIZE} / 2)$ or $(top2 = \text{MAXSIZE})$

• D. $top1 = top2 - 1$

Comments

This question was asked in BARC 2019

I couldn't add a tag to the question, probably because I don't have the question-editing privilege

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Typo

(Top1 < Top2)

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D is clear. :)

 

---------------------->    <----------------------------

                         T1   T2

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This also known as colliding strategy.

CS13002 : Assignment 7 (iitkgp.ac.in)

Answer 1

I think both A and D are correct.actually both defining same thing.

Comments

no Option D is variable in nature but A is fixed to mid point and adjacent to mid.

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got it. Thank you.

So D is the answer

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@anirudh SIR , Why not B?

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Sir, is the midpoint thing not efficient? What is the need for flexibility here?

Answer 2

A ) top1= ⎣MAXSIZE/2⎦

     top2= ⎣MAXSIZE/2⎦+1

Comments

That would limit the maximum size of each stack to be half of the array.