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Suppose a stack implementation supports, in addition to PUSH and POP, an operation REVERSE, which reverses the order of the elements on the stack.

  1. To implement a queue using the above stack implementation, show how to implement ENQUEUE using a single operation and DEQUEUE using a sequence of $3$ operations.
  2. The following post fix expression, containing single digit operands and arithmetic operators $+$ and $*$, is evaluated using a stack. 
    $5 \ 2 * 3 \ 4 + 5 \ 2 * * +$
    Show the contents of the stack
    1. After evaluating $5 \ 2 * 3 \ 4 +$
    2. After evaluating $5 \ 2 * 3 \ 4 + 5 \ 2$
    3. At the end of evaluation
asked in DS by Veteran (59.5k points)
edited by | 957 views

1 Answer

+23 votes
Best answer
  1. For enqueue push operation is sufficient
    For dequeue operation do the following
    -reverse, pop, reverse
     
  2. Contents of stack from top to bottom:

          i) $7 \ 10$
         ii) $2 \ 5 \ 7 \ 10$
         ii) $80$

answered by Boss (31.3k points)
edited by
0
Content of stack at end of evaluation should be empty?
0
for dequeue it should be reverse and pop are sufficient.

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