515.md

515. Find Largest Value in Each Tree Row

Solution 1 (time O(n), space O(n))

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    def largestValues(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """
        if not root:
            return []
        ans = [root.val]
        cur_node = [root]
        while cur_node:
            new_node = []
            new_val = []
            for node in cur_node:
                if node.left:
                    new_node.append(node.left)
                    new_val.append(node.left.val)
                if node.right:
                    new_node.append(node.right)
                    new_val.append(node.right.val)
            if len(new_val) > 0:
                ans.append(max(new_val))
            cur_node = new_node
        return ans