Given the root of a binary tree, find the maximum value v for which there exist different nodes a and b where v = |a.val - b.val| and a is an ancestor of b.
A node a is an ancestor of b if either: any child of a is equal to b or any child of a is an ancestor of b.
Example 1:
Input: root = [8,3,10,1,6,null,14,null,null,4,7,13]
Output: 7
Explanation: We have various ancestor-node differences, some of which are given below :
|8 - 3| = 5
|3 - 7| = 4
|8 - 1| = 7
|10 - 13| = 3
Among all possible differences, the maximum value of 7 is obtained by |8 - 1| = 7.
Example 2:
Input: root = [1,null,2,null,0,3]
Output: 3
Constraints:
- The number of nodes in the tree is in the range
[2, 5000]. -
0 <= Node.val <= 105
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 maxAncestorDiff(self, root: Optional[TreeNode]) -> int:
nodes = [(root, root.val, root.val)]
mdiff = 0
while len(nodes) > 0:
curr, currmin, currmax = nodes.pop()
mdiff = max(mdiff, currmax - currmin)
if curr.left:
nodes.append((curr.left, min(currmin, curr.left.val), max(currmax, curr.left.val)))
if curr.right:
nodes.append((curr.right, min(currmin, curr.right.val), max(currmax, curr.right.val)))
return mdiff
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