Coding for Interviews: Stack 2

stack.py

# A simple stack, LIFO fo' lyfe

class Node:
  def __init__(self, item, next):
		self.item = item
		self.next = next
	

class Stack: 
	top = None
	
	# put at item at the front of the stack
	def push(self, item):
		node = Node(item, self.top)
		self.top = node

	# remove the first item and return it
	def pop(self):
		old_top = self.top
		self.top = old_top.next
		old_top.next = None
		return old_top.item

	# sneak a look at the first item, but don't remove it
	def peek(self):
		return self.top.item

	def print_me(self):
		curr = self.top
		print "=== current stack ==="
		while curr != None:
			print curr.item
			curr = curr.next

def main():
	s = Stack()
	s.push("a")
	s.push("b")
	s.push("c")
	s.push("d")
	s.print_me()
	print s.pop()
	print s.pop()
	print s.peek()
	s.print_me()

if __name__ == '__main__':
    main()