Question

In Python 2) Design and implement a method for the stack class -discussed in class- that outputs -prints- the items in the stack from bottom to top with the condition that after the execution of this method the content of the stack is equal to the content of the stack before the method was called. You may assume that the items in the stack are printable. You cannot use any variables of any aggregate data types such as lists or sets or dictionaries etc.

Answer 1

Let the given stack be A. The approach would be to create another stack B, pop all elements in A and push them into B. Now pop and print each element in B and put them back in A. This would preserve the state of A.

---------------------------------------------

Please find the code below :

stackA = []

stackA.append(1)

stackA.append(2)

stackA.append(3)

stackA.append(4)

stackA.append(5)

print('Initial state of stackA: ')

print(stackA)

stackB = []

stackB.append(stackA.pop())

stackB.append(stackA.pop())

stackB.append(stackA.pop())

stackB.append(stackA.pop())

stackB.append(stackA.pop())

print('Printing elements of stackA in bottom up manner')

while len(stackB) > 0:

temp = stackB.pop()

print(temp)

stackA.append(temp)

print('Final state of stackA: ')

print(stackA)

----------------------------------------