MediumNo. 0814
Binary Tree Pruning — LeetCode 814 Python Solution
- Pattern
- Tree Traversal
- Topics
- Tree, Depth-First Search, Binary Tree
- Reading time
- 3 min
- Source
- leetcode.com
The problem
Given the root of a binary tree, return the same tree where every subtree (of the given tree) not containing a 1 has been removed. A subtree of a node node is node plus every node that is a descendant of node.
Example
- Input
- root = [1,null,0,0,1]
- Output
- [1,null,0,null,1]
- Explanation
- Only the red nodes satisfy the property "every subtree not containing a 1".
Python solution
# 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 pruneTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
if root is None:
return root
root.left = self.pruneTree(root.left)
root.right = self.pruneTree(root.right)
if root.val == 0 and root.left == root.right:
return None
return rootComplexity
- Time
- O(V+E)
- Space · auxiliary
- O(V)
Pattern: Tree Traversal
Choose the order — preorder, inorder, postorder, level — and the problem solves itself. LeetCode 814. Binary Tree Pruning is filed here because LeetCode tags it Tree and Binary Tree, which is the vocabulary this hub collects.
The tree traversal guide has the Python template for the pattern and the 225 LeetCode problems that use it.
Related problems
| No. | Problem | Difficulty |
|---|---|---|
| 0098 | Validate Binary Search Tree | Medium |
| 0099 | Recover Binary Search Tree | Medium |
| 0100 | Same Tree | Easy |
| 0101 | Symmetric Tree | Easy |
| 0104 | Maximum Depth of Binary Tree | Easy |
| 0110 | Balanced Binary Tree | Easy |
Frequently asked questions
- How hard is LeetCode 814. Binary Tree Pruning?
LeetCode 814. Binary Tree Pruning is rated Medium on LeetCode.
- What is the time complexity of LeetCode 814. Binary Tree Pruning?
The Python solution on this page runs in O(V+E).
- What is the space complexity of LeetCode 814. Binary Tree Pruning?
The Python solution on this page uses O(V) auxiliary space.
- What topics does LeetCode 814. Binary Tree Pruning cover?
LeetCode 814. Binary Tree Pruning is tagged Tree, Depth-First Search and Binary Tree on LeetCode.