1. Write a Python function that uses a Stack to reverse a list.  You
  can assume that the Stack class exists with all of the standard
  Stack operations: Stack, push, pop, peek, len, isEmpty.

def revWithStack (lst):
   stack = Stack()
   for x in lst:
       stack.push(x)
   newlst = []
   while not stack.isEmpty():
       newlst.append( stack.pop() )
   return newlst



>>> from Stack import *
>>> a = [1, 2, 3, 4]
>>> revWithStack(a)
[4, 3, 2, 1]


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2. Below are some constructors, accessors and mutators for a Node
  class and an UnorderedList class.  Write a method in the class to
  get the values from the UnorderedList (i.e., self) and create a
  regular Python list from the values. You should not destroy the
  original UnorderedList.

class Node:
    def __init__(self, initdata):
        self._data = initdata
        self._next = None

    def getData(self): ...
    def getNext(self): ...
    def setData(self, newdata): ...
    def setNext(self, newnext): ...

class UnorderedList:
    def __init__(self):
        self._head = None


    def toList(self):
        output = []
        ptr = self._head
	while ptr != None:
           output.append( ptr.getData() )
	   ptr = ptr.getNext()
        return output



>>> from Lists import *
>>> ul = UnorderedList()
>>> ul.addToFront(4)
>>> ul.addToFront('abc')
>>> ul.addToFront(17)
>>> ul.toList()
[17, 'abc', 4]


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3. Suppose you have the UnorderedList class with the standard
  operators: List, addToFront, get, remove, search, isEmpty, len.
  Show how you could use your UnorderedList class to implement the
  following Stack methods.  If there are other UnorderedList} methods
  that you need, show how you'd implement them.

  class StackWithLists:
     def __init__(self):
     def push(self, item):
     def pop(self):


In UnorderedList class:

     def removeFromFront(self):
         if not self.isEmpty():
             temp = self._head
             self._head = self._head.getNext()
             return temp.getData()
         else:
             return None

In StackWithLists class:

     def __init__(self):
         self._items = UnorderedList()

     def push(self, item):
         self._items.addToFront(item)

     def pop(self):
         return self._items.removeFromFront()



>>> from Lists import *
>>> swl = StackWithLists()
>>> swl.push(3)
>>> swl.push(1)
>>> swl.push(2)
>>> swl.pop()
2
>>> swl.pop()
1
>>> swl.pop()
3
>>> swl.pop()