Skip to content
Snippets Groups Projects
Select Git revision
  • 7d3b4c91cdd8bda28afe2307984b6a6573f28c36
  • master default protected
2 results

splay_operation_test.py

Blame
    • splay_operation.py 3.78 KiB
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75
    76
    77
    78
    79
    80
    81
    82
    83
    84
    85
    86
    87
    88
    89
    90
    91
    92
    93
    94
    95
    96
    97
    98
    99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119 
    

    

    

    #!/usr/bin/env python3

class Node:
    """Node in a binary tree `Tree`"""

    def __init__(self, key, left=None, right=None, parent=None):
        self.key = key
        self.parent = parent
        self.left = left
        self.right = right
        if left is not None: left.parent = self
        if right is not None: right.parent = self

class Tree:
    """A simple binary search tree"""

    def __init__(self, root=None):
        self.root = root

    def rotate(self, node):
        """ Rotate the given `node` up.

        Performs a single rotation of the edge between the given node
        and its parent, choosing left or right rotation appropriately.
        """
        if node.parent is not None:
            if node.parent.left == node:
                if node.right is not None: node.right.parent = node.parent
                node.parent.left = node.right
                node.right = node.parent
            else:
                if node.left is not None: node.left.parent = node.parent
                node.parent.right = node.left
                node.left = node.parent
            if node.parent.parent is not None:
                if node.parent.parent.left == node.parent:
                    node.parent.parent.left = node
                else:
                    node.parent.parent.right = node
            else:
                self.root = node
            node.parent.parent, node.parent = node, node.parent.parent

    def lookup(self, key):
        """Look up the given key in the tree.

        Returns the node with the requested key or `None`.
        """
        # TODO: Utilize splay suitably.
        node = self.root
        while node is not None:
            if node.key == key:
                return node
            if key < node.key:
                node = node.left
            else:
                node = node.right
        return None

    def insert(self, key):
        """Insert key into the tree.

        If the key is already present, nothing happens.
        """
        # TODO: Utilize splay suitably.
        if self.root is None:
            self.root = Node(key)
            return

        node = self.root
        while node.key != key:
            if key < node.key:
                if node.left is None:
                    node.left = Node(key, parent=node)
                node = node.left
            else:
                if node.right is None:
                    node.right = Node(key, parent=node)
                node = node.right

    def remove(self, key):
        """Remove given key from the tree.

        It the key is not present, nothing happens.
        """
        # TODO: Utilize splay suitably.
        node = self.root
        while node is not None and node.key != key:
            if key < node.key:
                node = node.left
            else:
                node = node.right

        if node is not None:
            if node.left is not None and node.right is not None:
                replacement = node.right
                while replacement.left is not None:
                    replacement = replacement.left
                node.key = replacement.key
                node = replacement

            replacement = node.left if node.left is not None else node.right
            if node.parent is not None:
                if node.parent.left == node: node.parent.left = replacement
                else: node.parent.right = replacement
            else:
                self.root = replacement
            if replacement is not None:
                replacement.parent = node.parent

    def splay(self, node):
        """Splay the given node.

        If a single rotation needs to be performed, perform it as the last rotation
        (i.e., to move the splayed node to the root of the tree).
        """
        # TODO: Implement
        raise NotImplementedError