1026. Maximum Difference Between Node and Ancestor

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

# @lc code=start
using LeetCode

function max_ancestor_diff(root::TreeNode{Int})
    res = 0
    function min_max_descendant(root::TreeNode{Int})
        minres, maxres = root.val, root.val
        for child in (:left, :right)
            cd_node = getproperty(root, child)
            isnothing(cd_node) && continue
            minl, maxl = min_max_descendant(cd_node)
            res = max(res, abs(root.val - minl), abs(root.val - maxl))
            minres = min(minres, minl)
            maxres = max(maxres, maxl)
        end
        return minres, maxres
    end
    min_max_descendant(root)
    return res
end
# @lc code=end

max_ancestor_diff (generic function with 1 method)

This page was generated using DemoCards.jl and Literate.jl.