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Exploratory implementation of red-black tree insertion in Python
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| RED = 'red' | |
| BLACK = 'black' | |
| class IterMixin(object): | |
| def __iter__(self): | |
| for attr, value in self.__dict__.iteritems(): | |
| yield attr, value | |
| class Tree: | |
| def __init__(self, root=None, nodes=set()): | |
| self.root = root | |
| self.nodes = nodes | |
| if root is not None: | |
| self.nodes.add(root) | |
| def insertNode(self, next_node, node): | |
| if node.key < next_node.key: | |
| if next_node.left is None: | |
| next_node.left = node | |
| node.parent = next_node | |
| else: | |
| self.insertNode(next_node.left, node) | |
| return | |
| if next_node.right is None: | |
| next_node.right = node | |
| node.parent = next_node | |
| else: | |
| self.insertNode(next_node.right, node) | |
| def addNode(self, node): | |
| self.nodes.add(node) | |
| self.insertNode(self.root, node) | |
| class RedBlackTree(Tree): | |
| def __init__(self, root=None, nodes=set()): | |
| self.root = root | |
| self.nodes = nodes | |
| if root is not None: | |
| self.nodes.add(root) | |
| self.root.color = BLACK | |
| def insertNode(self, next_node, node): | |
| if node.key < next_node.key: | |
| if next_node.left.isLeaf(): | |
| next_node.left = node | |
| node.parent = next_node | |
| else: | |
| self.insertNode(next_node.left, node) | |
| return | |
| if next_node.right.isLeaf(): | |
| next_node.right = node | |
| node.parent = next_node | |
| else: | |
| self.insertNode(next_node.right, node) | |
| def rotateLeft(self, node): | |
| parent = node.parent | |
| right_child = node.right | |
| right_child_left = right_child.left | |
| parent.right = right_child | |
| right_child.parent = parent | |
| right_child.left = node | |
| node.parent = right_child | |
| node.right = right_child_left | |
| right_child_left.parent = node | |
| if node is self.root: | |
| self.root = right_child | |
| def rotateRight(self, node): | |
| parent = node.parent | |
| left_child = node.left | |
| left_child_right = left_child.right | |
| parent.left = left_child | |
| left_child.parent = parent | |
| left_child.left = node | |
| node.parent = left_child | |
| node.left = left_child_right | |
| left_child_right.parent = node | |
| if node is self.root: | |
| self.root = right_child | |
| def balance(self, node): | |
| if node is not self.root: | |
| if node.parent is None: | |
| return | |
| if node.parent.color is BLACK: | |
| return | |
| if node.getGrandparent() is not None: | |
| grandparent = node.getGrandparent() | |
| uncle = node.getUncle() | |
| if uncle.color is RED: | |
| node.parent.color = BLACK | |
| uncle.color = BLACK | |
| grandparent.color = RED | |
| self.balance(grandparent) | |
| return | |
| elif node is node.parent.right and node.parent is grandparent.left: | |
| self.rotateLeft(node.parent) | |
| node = node.left | |
| elif node is node.parent.left and node.parent is grandparent.right: | |
| self.rotateRight(node.parent) | |
| node = node.right | |
| grandparent = node.getGrandparent() | |
| node.parent.color = BLACK | |
| grandparent.color = RED | |
| if node is node.parent.left: | |
| self.rotateRight(grandparent) | |
| else: | |
| self.rotateLeft(grandparent) | |
| self.root.color = BLACK | |
| def addNode(self, node): | |
| self.nodes.add(node) | |
| self.insertNode(self.root, node) | |
| self.balance(node) | |
| class Node(IterMixin): | |
| def __init__(self, key, parent=None, left=None, right=None): | |
| self.key = key | |
| self.parent = parent | |
| self.left = left | |
| self.right = right | |
| def getGrandparent(self): | |
| grandparent = None | |
| if self.parent is not None: | |
| grandparent = self.parent.parent | |
| return grandparent | |
| def getUncle(self): | |
| uncle = None | |
| if self.parent is not None and self.parent.parent is not None: | |
| if self.parent is self.getGrandparent().left: | |
| uncle = self.getGrandparent().right | |
| else: | |
| uncle = self.getGrandparent().left | |
| return uncle | |
| class Leaf(): | |
| def __init__(self, color=BLACK): | |
| self.key = None | |
| self.color = color | |
| def isLeaf(self): | |
| return True | |
| class RedBlackNode(Node): | |
| def __init__(self, key, color=RED, parent=None, left=Leaf(), right=Leaf()): | |
| self.key = key | |
| self.parent = parent | |
| self.left = left | |
| self.right = right | |
| self.color = color | |
| def isLeaf(self): | |
| return False | |
| node1 = RedBlackNode(13) | |
| tree = RedBlackTree(node1) | |
| values = [2, 15, 28, 5, 1, 30, 32] | |
| for val in values: | |
| new_node = RedBlackNode(val) | |
| tree.addNode(new_node) | |
| print('Root node is: %s' % tree.root.key) | |
| i = 1 | |
| for node in tree.nodes: | |
| print('Node %s:' % i) | |
| print('Address: %s' % node) | |
| for k,v in node: | |
| print('%s: %s' % (k,v)) | |
| print('------------------------') | |
| i+=1 |
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