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BinaryTree.py
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BinaryTree.py
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import unittest
__author__ = 'Minsuk Heo'
"""
Binary Tree
remove :
1) Node to be removed has no children.
This case is quite simple. Algorithm sets corresponding link of the parent to NULL and disposes the node.
2) Node to be removed has one child.
It this case, node is cut from the tree and algorithm links single child (with it's subtree) directly to the parent of the removed node.
3) Node to be removed has two children.
(1) find a minimum value in the right subtree;
(2) replace value of the node to be removed with found minimum. Now, right subtree contains a duplicate!
(3) apply remove to the right subtree to remove a duplicate.
"""
class Node:
def __init__(self, item):
self.val = item
self.left = None
self.right = None
class BinaryTree:
def __init__(self):
self.head = Node(None)
#test purpose lists
self.preorder_list = []
self.inorder_list = []
self.postorder_list = []
def search(self, item):
if self.head.val is None:
return False
else:
return self.__search_node(self.head, item)
def __search_node(self, cur, item):
if cur.val == item:
return True
else:
if cur.val >= item:
if cur.left is not None:
return self.__search_node(cur.left, item)
else:
return False
else:
if cur.right is not None:
return self.__search_node(cur.right, item)
else:
return False
def add(self, item):
if self.head.val is None:
self.head.val = item
else:
self.__add_node(self.head, item)
def __add_node(self, cur, item):
if cur.val >= item:
if cur.left is not None:
self.__add_node(cur.left, item)
else:
cur.left = Node(item)
else:
if cur.right is not None:
self.__add_node(cur.right, item)
else:
cur.right = Node(item)
def remove(self, item):
if self.head.val is None:
print ("there is no item: in BST", item)
if self.head.val == item:
# 1) Node to be removed has no children.
if self.head.left is None and self.head.right is None:
self.head = None
# 2) Node to be removed has one child.
elif self.head.left is None and self.head.right is not None:
self.head = self.head.right
# 3) Node to be removed has one child.
elif self.head.left is not None and self.head.right is None:
self.head = self.head.left
# 4) Node to be removed has two children.
else:
self.head.val = self.__most_left_val_from_right_node(self.head.right).val
self.__removeitem(self.head, self.head.right, self.head.val)
else:
if self.head.val > item:
self.__remove(self.head, self.head.left, item)
else:
self.__remove(self.head, self.head.right, item)
def __remove(self, parent, cur, item):
if cur is None:
print ("There is no item: ", item)
if cur.val == item:
# 1) Node to be removed has no children.
if cur.left is None and cur.right is None:
if parent.left == cur:
parent.left = None
else:
parent.right = None
# 2) Node to be removed has one child.
elif cur.left is None and cur.right is not None:
if parent.left == cur:
parent.left = cur.right
else:
parent.right = cur.right
# 3) Node to be removed has one child.
elif cur.left is not None and cur.right is None:
if parent.left == cur:
parent.left = cur.left
else:
parent.right = cur.left
# 4) Node to be removed has two children.
else:
cur.val = self.__most_left_val_from_right_node(cur.right).val
self.__removeitem(cur, cur.right, cur.val)
def __most_left_val_from_right_node(self, cur):
if cur.left is None:
return cur
else:
return self.__most_left_val_from_right_node(cur.left)
def __removeitem(self, parent, cur, item):
if cur.val == item:
if parent.left == cur:
parent.left = None
else:
parent.right = None
else:
if cur.val > item:
self.__removeitem(cur, cur.left, item)
else:
self.__removeitem(cur, cur.right, item)
def preorder_traverse(self):
if self.head is not None:
self.__preorder(self.head)
def __preorder(self, cur):
self.preorder_list.append(cur.val)
print (cur.val)
if cur.left is not None:
self.__preorder(cur.left)
if cur.right is not None:
self.__preorder(cur.right)
def inorder_traverse(self):
if self.head is not None:
self.__inorder(self.head)
def __inorder(self, cur):
if cur.left is not None:
self.__inorder(cur.left)
self.inorder_list.append(cur.val)
print (cur.val)
if cur.right is not None:
self.__inorder(cur.right)
def postorder_traverse(self):
if self.head is not None:
self.__postorder(self.head)
def __postorder(self, cur):
if cur.left is not None:
self.__postorder(cur.left)
if cur.right is not None:
self.__postorder(cur.right)
self.postorder_list.append(cur.val)
print (cur.val)
class binary_tree_test(unittest.TestCase):
def test(self):
bt = BinaryTree()
bt.add(5)
bt.add(3)
bt.add(4)
bt.add(1)
bt.add(7)
print("pre order")
bt.preorder_traverse()
self.assertEqual(bt.preorder_list, [5,3,1,4,7])
print("in order")
bt.inorder_traverse()
self.assertEqual(bt.inorder_list, [1,3,4,5,7])
print("post order")
bt.postorder_traverse()
self.assertEqual(bt.postorder_list, [1,4,3,7,5])
print ("bt root remove")
bt_root_remove_test = BinaryTree()
bt_root_remove_test.add(60)
bt_root_remove_test.add(50)
bt_root_remove_test.add(70)
bt_root_remove_test.remove(60)
bt_root_remove_test.preorder_traverse()
self.assertEqual(bt_root_remove_test.preorder_list, [70,50])
print ("bt root remove2")
bt_root_remove_test = BinaryTree()
bt_root_remove_test.add(60)
bt_root_remove_test.add(50)
bt_root_remove_test.remove(60)
bt_root_remove_test.preorder_traverse()
self.assertEqual(bt_root_remove_test.preorder_list, [50])
print ("bt root remove3")
bt_root_remove_test = BinaryTree()
bt_root_remove_test.add(60)
bt_root_remove_test.add(70)
bt_root_remove_test.remove(60)
bt_root_remove_test.preorder_traverse()
self.assertEqual(bt_root_remove_test.preorder_list, [70])
print ("bt left remove 1")
bt_left_remove_test_1 = BinaryTree()
bt_left_remove_test_1.add(60)
bt_left_remove_test_1.add(50)
bt_left_remove_test_1.add(70)
bt_left_remove_test_1.remove(50)
bt_left_remove_test_1.preorder_traverse()
self.assertEqual(bt_left_remove_test_1.preorder_list, [60,70])
print ("bt left remove 2")
bt_left_remove_test_2_left = BinaryTree()
bt_left_remove_test_2_left.add(60)
bt_left_remove_test_2_left.add(50)
bt_left_remove_test_2_left.add(70)
bt_left_remove_test_2_left.add(40)
bt_left_remove_test_2_left.remove(50)
bt_left_remove_test_2_left.preorder_traverse()
self.assertEqual(bt_left_remove_test_2_left.preorder_list, [60,40,70])
print ("bt right remove 2")
bt_left_remove_test_2_right = BinaryTree()
bt_left_remove_test_2_right.add(60)
bt_left_remove_test_2_right.add(50)
bt_left_remove_test_2_right.add(70)
bt_left_remove_test_2_right.add(55)
bt_left_remove_test_2_right.remove(50)
bt_left_remove_test_2_right.preorder_traverse()
self.assertEqual(bt_left_remove_test_2_right.preorder_list, [60,55,70])
print ("bt right remove 1")
bt_right_remove_test_1 = BinaryTree()
bt_right_remove_test_1.add(60)
bt_right_remove_test_1.add(50)
bt_right_remove_test_1.add(70)
bt_right_remove_test_1.remove(70)
bt_right_remove_test_1.preorder_traverse()
self.assertEqual(bt_right_remove_test_1.preorder_list, [60,50])
print ("bt right remove 2")
bt_right_remove_test_2_left = BinaryTree()
bt_right_remove_test_2_left.add(60)
bt_right_remove_test_2_left.add(50)
bt_right_remove_test_2_left.add(70)
bt_right_remove_test_2_left.add(65)
bt_right_remove_test_2_left.remove(70)
bt_right_remove_test_2_left.preorder_traverse()
self.assertEqual(bt_right_remove_test_2_left.preorder_list, [60,50,65])
print ("bt right remove 2")
bt_right_remove_test_2_right = BinaryTree()
bt_right_remove_test_2_right.add(60)
bt_right_remove_test_2_right.add(50)
bt_right_remove_test_2_right.add(70)
bt_right_remove_test_2_right.add(75)
bt_right_remove_test_2_right.remove(70)
bt_right_remove_test_2_right.preorder_traverse()
self.assertEqual(bt_right_remove_test_2_right.preorder_list, [60,50,75])
print ("bt left remove 3")
bt_left_remove_test_3 = BinaryTree()
bt_left_remove_test_3.add(60)
bt_left_remove_test_3.add(50)
bt_left_remove_test_3.add(70)
bt_left_remove_test_3.add(40)
bt_left_remove_test_3.add(55)
bt_left_remove_test_3.add(52)
bt_left_remove_test_3.remove(50)
bt_left_remove_test_3.preorder_traverse()
self.assertEqual(bt_left_remove_test_3.preorder_list, [60,52,40,55,70])
print("BST search test")
bt_search_test = BinaryTree()
bt_search_test.add(60)
bt_search_test.add(50)
bt_search_test.add(70)
bt_search_test.add(40)
bt_search_test.add(55)
bt_search_test.add(52)
self.assertTrue(bt_search_test.search(60))
self.assertTrue(bt_search_test.search(50))
self.assertTrue(bt_search_test.search(70))
self.assertTrue(bt_search_test.search(40))
self.assertTrue(bt_search_test.search(55))
self.assertTrue(bt_search_test.search(52))
self.assertFalse(bt_search_test.search(61))
self.assertFalse(bt_search_test.search(81))