Description
https://leetcode.com/problems/maximum-level-sum-of-a-binary-tree/
Given the root of a binary tree, the level of its root is 1, the level of its children is 2, and so on.
Return the smallest level x such that the sum of all the values of nodes at level x is maximal.
Example 1:
Input: root = [1,7,0,7,-8,null,null] Output: 2 Explanation: Level 1 sum = 1. Level 2 sum = 7 + 0 = 7. Level 3 sum = 7 + -8 = -1. So we return the level with the maximum sum which is level 2.
Example 2:
Input: root = [989,null,10250,98693,-89388,null,null,null,-32127] Output: 2
Constraints:
- The number of nodes in the tree is in the range
[1, 104]. -105 <= Node.val <= 105
Explanation
Conduct level order traverse and find out the level with the maximum sum.
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 maxLevelSum(self, root: Optional[TreeNode]) -> int:
if not root:
return 0
max_level_sum = -sys.maxsize
queue = []
queue.append(root)
levels = []
while queue:
size = len(queue)
level = []
for i in range(size):
node = queue.pop(0)
level.append(node.val)
if node.left:
queue.append(node.left)
if node.right:
queue.append(node.right)
levels.append(sum(level))
return levels.index(max(levels)) + 1- Time Complexity: O(N).
- Space Complexity: O(N).