LeetCode Top Interview 150
637. Average of Levels in Binary Tree
Easy
Given the root of a binary tree, return the average value of the nodes on each level in the form of an array. Answers within 10-5 of the actual answer will be accepted.
Example 1:
Input: root = [3,9,20,null,null,15,7]
Output: [3.00000,14.50000,11.00000] Explanation: The average value of nodes on level 0 is 3, on level 1 is 14.5, and on level 2 is 11. Hence return [3, 14.5, 11].
Example 2:
Input: root = [3,9,20,15,7]
Output: [3.00000,14.50000,11.00000]
Constraints:
- The number of nodes in the tree is in the range
[1, 104]. -231 <= Node.val <= 231 - 1
Solution
from typing import List, Optional, Dict
class TreeNode:
def __init__(self, val: int = 0, left: Optional['TreeNode'] = None, right: Optional['TreeNode'] = None):
self.val = val
self.left = left
self.right = right
class Solution:
def averageOfLevels(self, root: Optional[TreeNode]) -> List[float]:
q = [root]
ans = []
while q:
s = 0
nq = []
for u in q:
s += u.val
if u.left:
nq.append(u.left)
if u.right:
nq.append(u.right)
ans.append(s/len(q))
q = nq
return ans