1026.md

1026. Maximum Difference Between Node and Ancestor

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

# 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 maxAncestorDiff(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        def dfs(root, min_val, max_val):
            if root is None:
                return 0
            self.ans = max(self.ans, abs(min_val - root.val), abs(max_val - root.val))
            min_val = min(min_val, root.val)
            max_val = max(max_val, root.val)
            dfs(root.left, min_val, max_val)
            dfs(root.right, min_val, max_val)
            
        self.ans = 0
        dfs(root, root.val, root.val)
        return self.ans