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SQP3 Implementation Stack Using Queue

In this Problem Implementation Stack Using Queue we Implemrnt using Singh Stack abd Double Stack

We Know that the stack works Top to Down Approch

We Know that the Queue works Down to Top Approch

Using 2 Queue

Thougt Process

In Order to Implement the Stack using Queue we Required 2 Queue

push(x)

Add x to the Queue2

Put all the Element into the Queue1 -> Queue2

Swap Queue2 to Queue1

pop()

Remove the Top Element by Queue1

this is the Process Follow again and again

Notes

Note: Zoom for Better Understanding

Code Zone!

Time Complexity:O(N) Becouse all operation takes Time in Worst Case
Space Complexity:O(N)+O(N) Becouse we used a 2 Queue that's why.

But Interviewer Not happy this Solution Becouse we used 2 Queue Not Time To Optimized the Approch

Using 1 Queue

Intuition: As we know stack follows last in first out, which means we get the most recently inserted element whenever we remove an element from the stack. But queue follows first in first out, it means we get that element which we inserted in the starting at each deletion, it means if we want to use the queue like a stack we have to arrange elements in the queue such that we get the most recent element at each

Take a single queue.

push(x): Push the element in the queue.

Use a for loop of size()-1, remove element from queue and again push back to the queue, hence the most recent element becomes the most former element and vice versa.

pop(): remove the element from the queue.

top(): show the element at the top of the queue.

size(): size of the current queue.

Code Zone!

Time Complexity:O(N) Becouse all operation takes Time in Worst Case
Space Complexity:O(N)Becouse we used a 1 Queue that's why.