Stack implementation

Question

Comments

answer= 17, pls correct me if I'm wrong! ;)

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bilkul hi galat

 

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I am getting 60.5 ns as the answer. @ARUN_YADAV 1

Assume at t=0, the operations start. Push takes 5 ns and between each push operation there is a 1ns gap. So, by the end of the last element i.e 1 pushed to the stack the timestamp reads 47 ns.

Now, the first pop operation begins after 1ns of the last push. And each pop needs 10 ns. So the first pop operation is over by 47 + 1 + 10 ns = 58ns. The last pop operation removes 8 from the stack at timestamp 135 ns. 

Stack life of en element = End of push for element - Start of pop for element.

For each element , the stack life is as follows 
1 - 1ns
2 - 18 ns
3 - 35ns
4- 52ns
5 - 69ns
6 - 86ns
7- 103ns
8 - 120ns.

Computing average of above 8 entries gives 60.5ns as average stack life of an element in the given stack.

Answer 1

Answer: 17

 

Taking any one element, using bruteforce logic, as average is asked, lets take element '4',

 

Now, above 4; 

 

First, we need to push 3,2,1 which takes 15(push-operation delay) + 3(intermediate operation delay) = 18

 

And also, we need to consider its pop operations, as the life of the element in stack is defined by its presence, pop 1,2,3 

                              which takes  33(pop-operation delay) + 3(intermediate operation delay) = 33

 

We get (18+33)/3 {as we are considering 3 elements here (1,2,3)}   =  17

 

 

Similarly for other elements as well we would get a similar average lifespan. 

 

Answer 2

60.5 ns

Total stack time spent by all 8 elements is 484ns thus avg will be 60.5ns