1161. Maximum Level Sum of a Binary Tree

[fockspaces]

BFS 直接 level by level 掃 sum 即可

# 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:
        queue = [root]
        ans = level = 1
        max_sum = float('-inf')
        while queue:
            level_len, level_sum = len(queue), 0
            for _ in range(level_len):
                node = queue.pop(0)
                level_sum += node.val
                if node.left:
                    queue.append(node.left)
                if node.right:
                    queue.append(node.right)
            if max_sum < level_sum:
                max_sum = level_sum
                ans = level
            level += 1
        return ans