class BSTNode(object):
	def __init__(self, key, value, left=None, right=None):
		self.key,self.value,self.left,self.right = key,value,left,right



class BST(object):
	def __init__(self,root=None):
		self.root = root

	@classmethod
	def build_from(cls,node_list):
		cls.size = 0
		key_to_node_dict = {}
		for node_dict in node_list:
			key = node_dict['key']
			key_to_node_dict[key] = BSTNode(key, value=key)
		
		for node_dict in node_list:
			key = node_dict['key']
			node = key_to_node_dict[key]
			if node_dict['is_root']:
				root = node
			node.left = key_to_node_dict.get(node_dict['left'])
			node.right = key_to_node_dict.get(node_dict['right'])
		return cls(root)
	
	def _bst_search(self, subtree, key):
		if subtree is None:
			return None
		elif key < subtree.key:
			return self._bst_search(subtree.left, key)
		elif key > subtree.key:
			return self._bst_search(subtree.right, key)
		else:
			return subtree
	
	def get(self, key, default=None):
		node = self._bst_search(self.root, key)
		if node is None:
			return default
		else:
			return node.value
	
	def __cantains__(self,key):
		return self._bst_search(self.root, key) is not None

	def _bst_min_node(self, subtree):
		if subtree is None:
			return None
		elif subtree.left is None:
			return subtree
		else:
			return self._bst_min_node(subtree.left)
	
	def _bst_max_node(self, subtree):
		if subtree is None:
			return None
		elif subtree.right is None:
			return subtree
		else:
			return self._bst_max_node(subtree.right)

	def bst_min(self):
		node = self._bst_min_node(self.root)
		return node.value if node else None
	
	def bst_max(self):
		node = self._bst_max_node(self.root)
		return node.value if node else None
	
	def _bst_insert(self, subtree, key, value):
		if subtree is None:
			subtree = BSTNode(key, value)
		elif key < subtree.key:
			subtree.left = self._bst_insert(subtree.left, key, value)
		elif key > subtree.key:
			subtree.right = self._bst_insert(subtree.right, key, value)
		return subtree
	
	def add(self, key, value):
		node = self._bst_search(self.root, key)
		if node is not None:
			node.value = value
			return False
		else:
			self.root = self._bst_insert(self.root, key, value)
			self.size += 1
			return True
		
	def _bst_remove(self, subtree, key):
		if subtree is None:
			return None
		elif key < subtree.key:
			subtree.left = self._bst_remove(subtree.left, key)
			return subtree
		elif key > subtree.key:
			subtree.right = self._bst_remove(subtree.right, key)
			return subtree
		else:															#如果找到了要刪除的節點
			if subtree.left is None and subtree.right is None:			#是葉子
				return None
			elif subtree.left is None or subtree.right is None:			#單孩子
				if subtree.left is not None:
					return subtree.left									#返回孩子並更換父節點指向	
				else:
					return subtree.right
			else:														#雙孩子情況，尋找邏輯後繼並且替換被刪除節點
				successor_node = self._bst_min_node(subtree.right)
				subtree.key, subtree.value = successor_node.key, successor_node.value
				subtree.right = self._bst_remove(subtree.right, subtree.key)
				return subtree
	def remove(self, key):
		self.size -= 1
		return self._bst_remove(self.root, key)

NODE_LIST = [
	{'key':60, 'left':12, 'right':90, 'is_root':True},
	{'key':12, 'left':4, 'right':41, 'is_root':False},
	{'key':4, 'left':1, 'right':None, 'is_root':False},
	{'key':1, 'left':None, 'right':None, 'is_root':False},
	{'key':41, 'left':29, 'right':None, 'is_root':False},
	{'key':29, 'left':23, 'right':37, 'is_root':False},
	{'key':23, 'left':None, 'right':None, 'is_root':False},
	{'key':37, 'left':None, 'right':None, 'is_root':False},
	{'key':90, 'left':71, 'right':100, 'is_root':False},
	{'key':71, 'left':None, 'right':84, 'is_root':False},
	{'key':100, 'left':None, 'right':None, 'is_root':False},
	{'key':84, 'left':None, 'right':None, 'is_root':False},
]

def test_bst_tree():
	bst = BST.build_from(NODE_LIST)
	for node_dict in NODE_LIST:
		key = node_dict['key']
		assert bst.get(key) == key
	assert bst.get(-1) is None
	assert bst.bst_min() == 1
	bst.add(0,0)
	assert bst.bst_min() == 0
	bst.remove(12)
	assert bst.get(12) is None
	bst.remove(1)
	assert bst.get(1) is None
 

文章內容輸出來源：拉勾教育大資料高薪訓練營