MediumNo. 0366LeetCode Premium
Find Leaves of Binary Tree — LeetCode 366 Python Solution
- Pattern
- Tree Traversal
- Topics
- Tree, Depth-First Search, Binary Tree
- Reading time
- 4 min
- Source
- leetcode.com
The problem
Given the root of a binary tree, collect a tree's nodes as if you were doing this: Collect all the leaf nodes. Remove all the leaf nodes.
Example
- Input
- root = [1,2,3,4,5]
- Output
- [[4,5,3],[2],[1]]
- Explanation
- [[3,5,4],[2],[1]] and [[3,4,5],[2],[1]] are also considered correct answers since per each level it does not matter the order on which elements are returned.
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 findLeaves(self, root: Optional[TreeNode]) -> List[List[int]]:
def dfs(root: Optional[TreeNode]) -> int:
if root is None:
return 0
l, r = dfs(root.left), dfs(root.right)
h = max(l, r)
if len(ans) == h:
ans.append([])
ans[h].append(root.val)
return h + 1
ans = []
dfs(root)
return ansComplexity
- Time
- O(V+E)
- Space · auxiliary
- O(V)
Pattern: Tree Traversal
Choose the order — preorder, inorder, postorder, level — and the problem solves itself. LeetCode 366. Find Leaves of Binary Tree 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 366. Find Leaves of Binary Tree?
LeetCode 366. Find Leaves of Binary Tree is rated Medium on LeetCode.
- What is the time complexity of LeetCode 366. Find Leaves of Binary Tree?
The Python solution on this page runs in O(V+E).
- What is the space complexity of LeetCode 366. Find Leaves of Binary Tree?
The Python solution on this page uses O(V) auxiliary space.
- What topics does LeetCode 366. Find Leaves of Binary Tree cover?
LeetCode 366. Find Leaves of Binary Tree is tagged Tree, Depth-First Search and Binary Tree on LeetCode.
- Is LeetCode 366. Find Leaves of Binary Tree a premium problem?
Yes. LeetCode 366. Find Leaves of Binary Tree is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.