Stack

Consider the following sequence of operations on an empty stack.

push(54); push(52); pop(); push(55); push(62); s=pop();

Consider the following sequence of operations on an empty queue.

enqueue(21); enqueue(24); dequeue(); enqueue(28); enqueue(32); q=dequeue();

The value of s+q is ___________.

A stack is implemented with an array of { }^{\prime} A[0 \ldots N-1]^{\prime} and a variable \text { 'pos'. } The push and pop operations are defined by the following code.

 push (x)
    A[pos] <- x
    pos <- pos -1
end push
pop()
    pos <- pos+1
    return A[pos]
end pop

Which of the following will initialize an empty stack with capacity N for the above implementation?

Convert the pre-fix expression to in-fix -^{*}+A B C^{*}-D E+F G

Choose the equivalent prefix form of the following expression
(a+(b-c))^{\star}((d-e) /(f+g-h))

The best data structure to check whether an arithmetic expression has balanced parenthesis is a:

The following postfix expression with single digit operands is evaluated using a stack:
8 \ 2 \ 3 \ \;\hat{}\; / \ 2 \ 3 * + 5 \ 1 * -
Note that \hat{}\; is the exponentiation operator. The top two elements of the stack after the first * is evaluated are

If the sequence of operations - push (1), push (2), pop, push (1), push (2), pop, pop, pop, push (2), pop are performed on a stack, the sequence of popped out values

The result evaluating the postfix expression 10 5 + 60 6 / * 8 - is

The five items: A, B, C, D, and E are pushed in a stack, one after other starting from A. The stack is popped four items and each element is inserted in a queue. The 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

Suppose a stack implementation supports an instruction REVERSE, which reverses the order of elements on the stack, in addition to the PUSH and POP instructions. Which one of the following statements is TRUE with respect to this modified stack?