The five items A,B,C,D and E are pushed in a stack, one after the other starting from A. The stack is popped 4 times and each element is inserted in a queue. Then two elements are deleted from the queue and pushed back on the stack. now one item is popped from the stack. The popped Item is:OptionsBACD
Question
The five items A,B,C,D and E are pushed in a stack, one after the other starting from A. The stack is popped 4 times and each element is inserted in a queue. Then two elements are deleted from the queue and pushed back on the stack. now one item is popped from the stack. The popped Item is:OptionsBACD
Solution
The operations can be broken down as follows:
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Push A, B, C, D, E onto the stack. The stack now looks like this: E, D, C, B, A (with E on top and A at the bottom).
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Pop 4 times from the stack and enqueue each popped item. The stack now has just A, and the queue has E, D, C, B (with E at the front and B at the back).
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Dequeue twice from the queue and push each dequeued item onto the stack. The queue now has C, B and the stack has D, E, A (with D on top and A at the bottom).
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Pop once from the stack. The popped item is D. So, the answer is D.
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