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###### Question 6861 – Data-Structures
May 23, 2024

Consider a sequence a of elements a0 = 1, a1 = 5, a2 = 7, a3 = 8, a4 = 9, and a5 = 2. The following operations are performed on a stack S and a queue Q, both of which are initially empty.
I: push the elements of a from a0 to a5 in that order into S.
II: enqueue the elements of a from a0 to a5 in that order into Q.
III: pop an element from S.
IV: dequeue an element from Q.
V: pop an element from S.
VI: dequeue an element from Q.
VII: dequeue an element from Q and push the same element into S.
VIII: Repeat operation
VII three times. IX: pop an element from S. X: pop an element from S.
The top element of S after executing the above operations is _____?

Question 221 Explanation:
Given the sequence “a” of elements a0 = 1, a1 = 5, a2 = 7, a3 = 8, a4 = 9, and a5 = 2.
I: push the elements from a0 to a5 in that order into S.

II: enqueue the elements of a from a0 to a5 in that order into Q.

III: pop an element from S.

IV: dequeue an element from Q.

V: pop an element from S.

VI: dequeue an element from Q.

VII: dequeue an element from Q and push the same element into S.
Element “7” is deleted and inserted into stack “S”

VIII: Repeat operation VII three times.
After performing the VIII operation , the elements of stack are as shown below

IX: pop an element from S.

X: pop an element from S

The top element of S after executing the above operations is 8.

8