Python3 Linked List Problem

The difference between two sets A and B is defined as the set containing elements of A that are not elements of B. For example, the difference of the sets {1, 2, 3} and {2, 3} is {1}.

def set_diff(a, b): """ Returns a set containing the elements of a that are not elements of b.

>>> res = set_diff(Link('a', Link('b')), Link(1, Link(2))) >>> len(res) 2 >>> set_contains(res, 'a') True >>> set_contains(res, 'b') True

>>> res = set_diff(Link('a', Link('b')), Link('b', Link(2))) >>> len(res) 1 >>> set_contains(res, 'a') True >>> set_contains(res, 'b') False

>>> set_diff(Link('a', Link('b', Link('c'))), Link('c', Link('a', Link('b')))) is Link.empty True

>>> set_diff(Link.empty, Link(1)) is Link.empty True

>>> set_diff(Link('lab10'), Link.empty).first 'lab10' """ """YOUR CODE GOES HERE"""

class Link: A Linked list with a first element and the rest." empty( def _init_(self, first, rest-empty): assert rest is Link.empty or isinstance(rest, Link) self.first first self.rest rest def_getitem(self, i): return self.first else: return self.rest [i-1] def len_(self) return 1 +len(self.rest) def-repr--(self): if self.rest is Link.empty: return 'Link(+ repr(self.first)+ return Link(' + repr(self.first) + + repr(self.rest) + ') def set_contains (s, v): "Return True if and only if set s contains v." if s is Link.empty: return False elif s.first V: return True else: return set_contains (s.rest, v) class Link: A Linked list with a first element and the rest." empty( def _init_(self, first, rest-empty): assert rest is Link.empty or isinstance(rest, Link) self.first first self.rest rest def_getitem(self, i): return self.first else: return self.rest [i-1] def len_(self) return 1 +len(self.rest) def-repr--(self): if self.rest is Link.empty: return 'Link(+ repr(self.first)+ return Link(' + repr(self.first) + + repr(self.rest) + ') def set_contains (s, v): "Return True if and only if set s contains v." if s is Link.empty: return False elif s.first V: return True else: return set_contains (s.rest, v)