class Set: | |
def __init__(self): | |
self.elts = {} | |
def add(self, elt): | |
self.elts[elt] = elt | |
def items(self): | |
return self.elts.keys() | |
def has_elt(self, elt): | |
return self.elts.has_key(elt) | |
class Stack: | |
def __init__(self): | |
self.stack = [] | |
self.pop = self.stack.pop | |
def push(self, elt): | |
self.stack.append(elt) | |
def top(self): | |
return self.stack[-1] |