Find largest value in each tree row

# 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 largestValues(self, root: Optional[TreeNode]) -> List[int]:
        if not root:
            return root
        queue = deque([root])
        res = []
        while queue:
            size = len(queue)
            tmp = -math.inf

            for i in range(size):
                node = queue.popleft()
                tmp = max(tmp, node.val)

                if node.left:
                    queue.append(node.left)
                if node.right:
                    queue.append(node.right)

            res.append(tmp)

        return res

Find Largest Value in Each Tree Row

Difficulty: Medium

Given the root of a binary tree, return an array of the largest value in each row of the tree (0-indexed).

 

Example 1:

Input: root = [1,3,2,5,3,null,9]
Output: [1,3,9]

Example 2:

Input: root = [1,2,3]
Output: [1,3]

 

Constraints:

  • The number of nodes in the tree will be in the range [0, 104].
  • -231 <= Node.val <= 231 - 1