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Update bst.py
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  • Ch06. Trees and Tree Algorithms/bst

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+128
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‎Ch06. Trees and Tree Algorithms/bst/bst.py‎

Lines changed: 128 additions & 119 deletions
Original file line numberDiff line numberDiff line change
@@ -1,180 +1,189 @@
1+
12
from treenode import TreeNode
23

3-
class AVLTree:
4+
class BinarySearchTree:
45
def __init__(self):
56
self.root: TreeNode = None
6-
self.size = 0
7+
self._size: int = 0
8+
9+
def size(self)->int:
10+
return self._size
711

812
def isEmpty(self)->bool:
9-
return self.root == None
13+
return self.root is None
1014

1115
def put(self, key):
1216
if self.root is None:
1317
self.root = TreeNode(key)
14-
elif self.root.key == key:
15-
self.root.key = key
16-
else:
17-
self.putHelper(self.root, key)
18-
19-
def putHelper(self, node: TreeNode, key): # helper method
20-
if node.key == key:
21-
return
22-
self.size += 1
23-
if node.key > key:
24-
if node.hasLeftChild():
25-
self.putHelper(node.leftChild, key)
26-
else:
27-
node.leftChild = TreeNode(key, node)
18+
self._size += 1
2819
else:
29-
if node.hasRightChild():
30-
self.putHelper(node.rightChild, key)
20+
self._put(self.root, key)
21+
22+
def _put(self, root: TreeNode, key):
23+
if root.key == key:
24+
root.key = key
25+
elif key < root.key:
26+
if root.hasLeftChild():
27+
self._put(root.leftChild, key)
28+
else:
29+
root.leftChild = TreeNode(key, root)
30+
self._size += 1
31+
else:
32+
if root.hasRightChild():
33+
self._put(root.rightChild, key)
3134
else:
32-
node.rightChild = TreeNode(key, node)
33-
35+
root.rightChild = TreeNode(key, root)
36+
self._size += 1
37+
3438
def get(self, key)->TreeNode:
3539
if self.root is None:
3640
return None
3741
else:
38-
return self.getHelper(self.root, key)
39-
40-
def getHelper(self, node: TreeNode, key): # helper method
41-
if node.key == key:
42-
return node
43-
elif node.key > key:
44-
if node.hasLeftChild():
45-
return self.getHelper(node.leftChild, key)
42+
return self._get(self.root, key)
43+
44+
def _get(self, root: TreeNode, key)->TreeNode:
45+
if root.key == key:
46+
return root
47+
elif key < root.key:
48+
if root.hasLeftChild():
49+
return self._get(root.leftChild, key)
4650
else:
4751
return None
4852
else:
49-
if node.hasRightChild():
50-
return self.getHelper(node.rightChild, key)
53+
if root.hasRightChild():
54+
return self._get(root.rightChild, key)
5155
else:
5256
return None
57+
'''
58+
def contains(self, key)->bool:
59+
if self.root is None:
60+
return False
61+
else:
62+
return self._contains(self.root, key)
63+
64+
def _contains(self, root: TreeNode, key)->bool:
65+
if root.key == key:
66+
return True
67+
elif key < root.key:
68+
if root.hasLeftChild():
69+
return self._contains(root.leftChild, key)
70+
else:
71+
return False
72+
else:
73+
if root.hasRightChild():
74+
return self._contains(root.rightChild, key)
75+
else:
76+
return False
77+
'''
78+
def contains(self, key)->bool:
79+
if self.root is None:
80+
return False
81+
else:
82+
found: bool = False
83+
node: TreeNode = self.root
84+
while node is not None and not found:
85+
if node.key == key:
86+
found = True
87+
elif key < node.key:
88+
node = node.leftChild
89+
else:
90+
node = node.rightChild
91+
return found
5392

5493
def delete(self, key):
94+
if self.isEmpty():
95+
return None
5596
toDelete: TreeNode = self.get(key)
5697
if toDelete is None:
5798
return
58-
self.size -= 1
99+
self._size -= 1
59100
if toDelete == self.root:
60101
if toDelete.isLeaf():
61102
self.root = None
62103
elif toDelete.hasBothChildren():
63-
maxNode: TreeNode = self.root.leftChild.findMax()
64-
tmpKey = maxNode.key
104+
minNode: TreeNode = toDelete.rightChild.findMin()
105+
tmpKey = minNode.key
65106
self.delete(tmpKey)
66107
self.root.key = tmpKey
67-
elif toDelete.hasLeftChild():
68-
self.root = self.root.leftChild
69108
else:
70-
self.root = self.root.rightChild
109+
if toDelete.hasLeftChild():
110+
self.root = self.root.leftChild
111+
self.root.parent = None
112+
else:
113+
self.root = self.root.rightChild
114+
self.root.parent = None
71115
else:
72-
parent: TreeNode = toDelete.parent
73116
if toDelete.isLeaf():
74117
if toDelete.isLeftChild():
75-
parent.leftChild = None
118+
toDelete.parent.leftChild = None
76119
else:
77-
parent.rightChild = None
120+
toDelete.parent.rightChild = None
78121
elif toDelete.hasBothChildren():
79-
maxNode: TreeNode = toDelete.leftChild.findMax()
80-
tmpKey = maxNode.key
122+
minNode: TreeNode = toDelete.rightChild.findMin()
123+
tmpKey = minNode.key
81124
self.delete(tmpKey)
82125
toDelete.key = tmpKey
83-
elif toDelete.hasLeftChild():
84-
if toDelete.isLeftChild():
85-
parent.leftChild = toDelete.leftChild
86-
toDelete.leftChild.parent = parent
87-
else:
88-
parent.rightChild = toDelete.leftChild
89-
toDelete.leftChild.parent = parent
90126
else:
91-
if toDelete.isLeftChild():
92-
parent.leftChild = toDelete.rightChild
93-
toDelete.rightChild.parent = parent
127+
if toDelete.hasLeftChild():
128+
if toDelete.isLeftChild():
129+
toDelete.parent.leftChild = toDelete.leftChild
130+
toDelete.leftChild.parent = toDelete.parent
131+
else:
132+
toDelete.parent.rightChild = toDelete.leftChild
133+
toDelete.leftChild.parent = toDelete.parent
94134
else:
95-
parent.rightChild = toDelete.rightChild
96-
toDelete.rightChild.parent = parent
97-
98-
def contains(self, key)->bool:
99-
if self.root is None:
100-
return False
101-
else:
102-
node: TreeNode = self.root
103-
found: bool = False
104-
while node is not None and not found:
105-
if node.key == key:
106-
found = True
107-
elif node.key < key:
108-
node = node.rightChild
109-
else:
110-
node = node.leftChild
111-
return found
112-
113-
def length(self)->int:
114-
return self.size
115-
116-
def findMin(self)->TreeNode:
117-
if self.root is None:
135+
if toDelete.isLeftChild():
136+
toDelete.parent.leftChild = toDelete.rightChild
137+
toDelete.rightChild.parent = toDelete.parent
138+
else:
139+
toDelete.parent.rightChild = toDelete.rightChild
140+
toDelete.rightChild.parent = toDelete.parent
141+
142+
def findMin(self)->TreeNode:
143+
if self.isEmpty():
118144
return None
119145
else:
120146
node: TreeNode = self.root
121147
while node.leftChild is not None:
122148
node = node.leftChild
123149
return node
124-
150+
125151
def findMax(self)->TreeNode:
126-
if self.root is None:
152+
if self.isEmpty():
127153
return None
128154
else:
129155
node: TreeNode = self.root
130156
while node.rightChild is not None:
131157
node = node.rightChild
132158
return node
133159

134-
def inorder(self):
135-
if self.root is not None:
136-
self.root.inorder()
137-
print()
138-
139-
140-
avl = AVLTree()
141-
avl.put(15)
142-
avl.put(50)
143-
avl.put(7)
144-
avl.put(8)
145-
avl.put(1)
146-
avl.put(9)
147-
148-
avl.inorder()
149-
print(avl.root.key)
150-
print(avl.root.rightChild.key)
151-
print(avl.root.rightChild.leftChild.key)
152-
153-
154-
'''
155-
avl.put(15)
156-
avl.put(7)
157-
avl.put(8)
158-
avl.put(6)
159-
avl.put(30)
160-
avl.put(20)
161-
avl.put(40)
162-
avl.put(18)
163-
avl.put(19)
164-
avl.put(25)
165-
avl.put(24)
166-
avl.put(17)
167-
avl.put(3)
168-
160+
169161

170-
print("contains #############")
171-
print(avl.contains(8), avl.contains(19), avl.contains(1101))
172-
print("Min ",avl.findMin().key, ", max ", avl.findMax().key)
173162

163+
bst = BinarySearchTree()
164+
bst.put(15)
165+
bst.put(7)
166+
bst.put(8)
167+
bst.put(6)
168+
bst.put(30)
169+
bst.put(20)
170+
bst.put(40)
171+
bst.put(18)
172+
bst.put(19)
173+
bst.put(25)
174+
bst.put(24)
175+
bst.put(17)
176+
bst.put(3)
174177

178+
print(bst.root.key)
179+
print(bst.root.rightChild.key)
175180

181+
print("contains #############")
182+
print(bst.contains(8), bst.contains(19), bst.contains(1101))
183+
print("Min ",bst.findMin().key, ", max ", bst.findMax().key)
176184
print("delete node with value 20 - has both children")
177-
avl.inorder()
178-
avl.delete(20)
179-
avl.inorder()
180-
'''
185+
186+
print(bst.contains(20))
187+
bst.delete(20)
188+
print(bst.contains(20))
189+

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