Merge pull request wangzheng0822#147 from jerryderry/binary-search-tree-python

binary search tree in python

Author: wangzheng0822

python/24_tree/binary_search_tree.py

@@ -0,0 +1,64 @@
+"""
+ Binary search tree
+
+ Author: Wenru Dong
+"""
+from typing import Optional
+
+class TreeNode:
+ def __init__(self, value: int):
+ self.val = value
+ self.left = None
+ self.right = None
+
+class BinarySearchTree:
+ def __init__(self):
+ self._root = None
+ 
+ def find(self, value: int) -> Optional[TreeNode]:
+ node = self._root
+ while node and node.val != value:
+ node = node.left if node.val > value else node.right
+ return node
+ 
+ def insert(self, value: int):
+ if not self._root:
+ self._root = TreeNode(value)
+ return
+ parent = None
+ node = self._root
+ while node:
+ parent = node
+ node = node.left if node.val > value else node.right
+ new_node = TreeNode(value)
+ if parent.val > value:
+ parent.left = new_node
+ else:
+ parent.right = new_node
+
+ def delete(self, value: int):
+ node = self._root
+ parent = None
+ while node and node.val != value:
+ parent = node
+ node = node.left if node.val > value else node.right
+ if not node: return
+ 
+ # 要删除的节点有两个子节点
+ if node.left and node.right:
+ successor = node.right
+ successor_parent = node
+ while successor.left:
+ successor_parent = successor
+ successor = successor.left
+ node.val = successor.val
+ parent, node = successor_parent, successor
+ 
+ # 删除节点是叶子节点或者仅有一个子节点
+ child = node.left if node.left else node.right
+ if not parent:
+ self._root = child
+ elif parent.left == node:
+ parent.left = child
+ else:
+ parent.right = child