test series

Question

Consider implementation of stack using queue by following algorithm.
Let x be an element to be pushed in the stack.
push(q1, x) {
    EQ(q1,x)
    
    while (q1 does not contain 1 element) {
k= DQ(q1)
EQ(q1,k)
           }
}
pop(q1) {
    DQ(q1)
}

How many enqueue and dequeue operations required to push 2 and pop 2 elements in the empty stack?

Comments

EQ = 3

DQ = 3

 

push (1)  - EQ -1 (While condition false)

push (2) - EQ -2 (While condition true - k = DQ(1), EQ(1) hence EQ = 3, DQ =1)

 

pop()

DQ(2) - DQ =2

DQ(1) - DQ = 3

 

total EQ =3, DQ =3

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thanks got it!

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@Ashwin Kulkarni but the condition of while loop never false for second-time insertion. Because when you Enqueue 2 (after enqueuing 1) then while condition will be checked and since it contains two elements so condition is true, then it will dequeue 1 and in that iteration only it will insert again 1, now at the end of this insertion while condition is checked and this time also queue contains two elements again condition true, and again repeat.