[+] A1 Starter Files

assignments/A1/a1_part1.py

@@ -0,0 +1,132 @@
+"""CSC111 Winter 2021 Assignment 1: Linked Lists, Part 1
+
+Instructions (READ THIS FIRST!)
+===============================
+
+This Python module contains three linked list subclasses corresponding to the three
+moving heuristics described on the assignment handout.
+
+You need to complete their implementations by overriding the __contains__ method
+(and only for CountLinkedList, additional methods as required).
+
+Copyright and Usage Information
+===============================
+
+This file is provided solely for the personal and private use of students
+taking CSC111 at the University of Toronto St. George campus. All forms of
+distribution of this code, whether as given or with any changes, are
+expressly prohibited. For more information on copyright for CSC111 materials,
+please consult our Course Syllabus.
+
+This file is Copyright (c) 2021 David Liu and Isaac Waller.
+"""
+from __future__ import annotations
+from dataclasses import dataclass
+from typing import Any, Optional
+
+from a1_linked_list import LinkedList, _Node
+
+
+################################################################################
+# Heuristic 1 (move to front)
+################################################################################
+class MoveToFrontLinkedList(LinkedList):
+    """A linked list implementation that uses a "move to front" heuristic for searches.
+
+    Representation Invariants:
+        - all items in this linked list are unique
+    """
+    def __contains__(self, item: Any) -> bool:
+        """Return whether item is in this linked list.
+
+        If the item is found, move it to the front of this list.
+
+        >>> linky = MoveToFrontLinkedList([10, 20, 30, 40, 50, 60])
+        >>> linky.__contains__(40)
+        True
+        >>> linky.to_list()
+        [40, 10, 20, 30, 50, 60]
+        """
+
+
+################################################################################
+# Heuristic 2 (swap)
+################################################################################
+class SwapLinkedList(LinkedList):
+    """A linked list implementation that uses a "swap" heuristic for searches.
+
+    Representation Invariants:
+        - all items in this linked list are unique
+    """
+    def __contains__(self, item: Any) -> bool:
+        """Return whether item is in this linked list.
+
+        If the item is found, swap it with the item before it, if any.
+        You may do this by reassigning _Node item or next attributes (or both).
+
+        >>> linky = SwapLinkedList([10, 20, 30, 40, 50, 60])
+        >>> linky.__contains__(40)
+        True
+        >>> linky.to_list()
+        [10, 20, 40, 30, 50, 60]
+        """
+
+
+################################################################################
+# Heuristic 3 (count)
+################################################################################
+# NOTE: this heuristic requires a new kind of _Node that has an additional "count" attribute.
+@dataclass
+class _CountNode(_Node):
+    """A node in a CountLinkedList.
+
+    Instance Attributes:
+      - item: The data stored in this node.
+      - next: The next node in the list, if any.
+      - access_count: The number of times this node has been accessed (used by the count heuristic)
+    """
+    next: Optional[_CountNode] = None
+    access_count: int = 0
+
+
+class CountLinkedList(LinkedList):
+    """A linked list implementation that uses a "swap" heuristic for searches.
+
+    Representation Invariants:
+        - all items in this linked list are unique
+        - nodes are sorted in non-increasing order by access_count
+
+    NOTE: In order to make use of the _CountNode class above, you'll need to override every
+    LinkedList method in a1_linked_list.py that creates new _Node objects to create _CountNode
+    objects instead. Your code for the overridden methods should be otherwise identical.
+    """
+    _first: Optional[_CountNode]
+
+    def __contains__(self, item: Any) -> bool:
+        """Return whether item is in this linked list.
+
+        If the item is found, increase its count and reorder the nodes in
+        non-increasing count order---see assignment handout for details.
+
+        >>> linky = CountLinkedList([10, 20, 30, 40, 50, 60])
+        >>> linky.__contains__(40)
+        True
+        >>> linky.to_list()
+        [40, 10, 20, 30, 50, 60]
+        """
+
+
+if __name__ == '__main__':
+    import python_ta
+    python_ta.check_all(config={
+        'max-line-length': 100,
+        'disable': ['E1136'],
+        'extra-imports': ['a1_linked_list'],
+        'max-nested-blocks': 4
+    })
+
+    import python_ta.contracts
+    python_ta.contracts.check_all_contracts()
+
+    import doctest
+    doctest.testmod()