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Data Structure-Stack

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We want to reverse elements of stack using a queue.Suppose stack operations,push and pop take 1 unit of time each and queue operations insert and delete take 2 units of time each.Assume n elements are there in the stack.The minimum time to reverse the stack is

(A) 4n units

(B) 6n units

(C) 8n units

(D) 9n units

1 Answer

3 3 votes
(B) 6n units is the answer.

Lets take an example the stack is having n elements present in it. Now to reverse them using queue we have to perform two steps n times.

1. pop the element from the stack and insert it to the queue . This will take n+2n time units respectively.

2.delete the element from the queue and push it into stack.This will take 2n+n time units respectively.

so the total time = 3n+3n=6n
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