Delete Node in a BST — LeetCode 450 Python Solution
MediumTreeBinary Search TreeBinary Tree
- Problem
- #450
- Pattern
- Tree Traversal
- Reading time
- 5 min
- Source
- leetcode.com
The problem
Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return the root node reference (possibly updated) of the BST.
Example
- Input
- root = [5,3,6,2,4,null,7], key = 3
- Output
- [5,4,6,2,null,null,7]
- Explanation
- Given key to delete is 3. So we find the node with value 3 and delete it.
Python solution
Python
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def deleteNode(self, root: Optional[TreeNode], key: int) -> Optional[TreeNode]:
if root is None:
return None
if root.val > key:
root.left = self.deleteNode(root.left, key)
return root
if root.val < key:
root.right = self.deleteNode(root.right, key)
return root
if root.left is None:
return root.right
if root.right is None:
return root.left
node = root.right
while node.left:
node = node.left
node.left = root.left
root = root.right
return rootComplexity
| Measure | Complexity |
|---|---|
| Time | O(n) |
| Space | O(h) auxiliary |
Pattern: Tree Traversal
Choose the order — preorder, inorder, postorder, level — and the problem solves itself. LeetCode 450. Delete Node in a BST is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Tree, Binary Tree and Binary Search Tree.
The tree traversal guide has the Python template for the pattern and the 225 LeetCode problems that use it.
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On a study list
This problem is on LeetCode 75.
Frequently asked questions
- How hard is LeetCode 450. Delete Node in a BST?
- LeetCode 450. Delete Node in a BST is rated Medium on LeetCode.
- What is the time complexity of LeetCode 450. Delete Node in a BST?
- The Python solution on this page runs in O(n).
- What is the space complexity of LeetCode 450. Delete Node in a BST?
- The Python solution on this page uses O(h) auxiliary space.
- What topics does LeetCode 450. Delete Node in a BST cover?
- LeetCode 450. Delete Node in a BST is tagged Tree, Binary Search Tree and Binary Tree on LeetCode.