題目
https://www.lintcode.com/problem/remove-node-in-binary-search-tree/description?_from=ladder&&fromId=2
實現
- 先中序遍歷一次樹,過濾掉要刪掉的節點
- 用中序遍歷的結果重新構造一新樹,返回新樹 root
代碼
class TreeNode:
def __init__(self, val):
self.val = val
self.left, self.right = None, None
class Solution:
"""
@param: root: The root of the binary search tree.
@param: value: Remove the node with given value.
@return: The root of the binary search tree after removal.
"""
inorder_results = []
def removeNode(self, root, value):
# 獲取中序遍歷結果
self.inorder(root, value)
# 用中序遍歷結果重新構造樹
new_root = self.build_tree(0, len(self.inorder_results) - 1)
return new_root
def inorder(self, root, value):
if root is None:
return
self.inorder(root.left, value)
if root.val != value:
self.inorder_results.append(root.val)
self.inorder(root.right, value)
def build_tree(self, left, right):
if left == right:
return TreeNode(self.inorder_results[left])
if left > right:
return None
mid = (left + right) // 2
node = TreeNode(self.inorder_results[mid])
node.left = self.build_tree(left, mid - 1)
node.right = self.build_tree(mid + 1, right)
return node