main.py

# define a Stack data structure
class Stack:
    def __init__(self):
        self.items = []

    def push(self,item):
        self.items.append(item)

    def pop(self):
        return self.items.pop()

    def peek(self):
        return self.items[len(self.items)-1]

    def size(self):
        return len(self.items)

# solution for question 1
def Stack1():
    s = Stack()
    actions = list("A*BCE**F*GH***I*")
    result = []
    for i in actions:
        if i == "*":
            s.pop()
            continue
        s.push(i)

    print("Stack1 solution:",result)

# solution for question 2
# since we have the input and output data predefined
# we can use dynamic programming and reverse engineer 
# from the output data to get the list of actions

def Stack2():
    s = Stack()
    actions = []
    res = []
    start = list("ABCDEF")
    end = list("BADECF")
    counter = len(start)

    while len(res)!= counter:
        if s.size() > 0 and s.peek() == end[0]:
            res.append(s.pop())
            actions.append("pop")
            end.pop(0)
            continue 
        s.push(start.pop(0))
        actions.append("push")
    print("Stack2 soultion:")
    print(actions)
    
Stack1()    
Stack2()