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172 lines
3.4 KiB
172 lines
3.4 KiB
class Node():
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def __init__(self,key):
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self.key = key
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self.left = None
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self.right = None
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self.parent = None
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class Tree():
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def __init__(self):
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self.root = None
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def add_node(self,key,node=None):
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if node is None:
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node = self.root
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if self.root is None:
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self.root = Node(key)
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else:
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if key <= node.key :
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if node.left is None:
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node.left = Node(key)
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node.left.parent = node
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print "left"
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return
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else:
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# return self.add_node(key,node = self.root.left)
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return self.add_node(key,node = node.left)
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else:
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if node.right is None:
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node.right = Node(key)
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node.right.parent = node
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print "right"
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return
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else:
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# return self.add_node(key,node = self.root.right)
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return self.add_node(key,node = node.right)
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def search(self,key,node = None):
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if node is None:
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node = self.root
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if self.root.key == key:
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print "key is at the root"
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return self.root
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else:
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if node.key == key :
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print "key exists"
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return node
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elif key < node.key and node.left is not None:
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print "left"
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return self.search(key,node = node.left)
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elif key > node.key and node.right is not None:
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print "right"
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return self.search(key,node = node.right)
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else:
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print "key does not exist"
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return None
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def delete_node(self,key,node=None):
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#search for the node to be deleted in tree
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if node is None:
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node = self.search(key)#return the node to be deleted
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#root has no parent node
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if self.root.key == node.key: #if it is root
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parent_node = self.root
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else:
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parent_node = node.parent
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'''case 1: The node has no chidren'''
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if node.left is None and node.right is None:
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if key <= parent_node.key:
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parent_node.left = None
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else:
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parent_node.right = None
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return
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'''case 2: The node has children'''
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''' if it has a single left node'''
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if node.left is not None and node.right is None :
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if node.left.key < parent_node.key :
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parent_node.left = node.left
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else:
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parent_node.right = node.left
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return
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'''if it has a single right node'''
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if node.right is not None and node.left is None:
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if node.key <= parent_node.key:
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parent_node.left = node.right
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else:
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parent_node.right = node.right
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return
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'''if it has two children'''
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'''find the node with the minimum value from the right subtree.
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copy its value to thhe node which needs to be removed.
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right subtree now has a duplicate and so remove it.'''
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if node.left is not None and node.right is not None:
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min_value = self.find_minimum(node)
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node.key = min_value.key
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min_value.parent.left = None
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return
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def find_minimum(self,node = None):
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if node is None:
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node = self.root
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'''find mimimum value from the right subtree'''
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'''case when there is only a root node'''
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if node.right is not None:
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node = node.right
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else:
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return node
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if node.left is not None:
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return self.find_minimum(node = node.left)
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else:
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return node
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def tree_data(self,node=None):
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if node is None:
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node = self.root
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stack = []
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while stack or node:
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if node is not None:
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stack.append(node)
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node = node.left
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else:
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node = stack.pop()
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yield node.key
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node = node.right
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t=Tree()
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t.add_node(10)
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t.add_node(13)
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t.add_node(14)
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t.add_node(8)
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t.add_node(9)
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t.add_node(7)
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t.add_node(11)
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'''
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10---8---7
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| ---9
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---13---11
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---14
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'''
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