Maximum Difference Between Node and Ancestor

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

Solutions

🧠 Cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution
{
    int max_check_value(TreeNode* root, int val)
    {
        if(!root)
            return 0;
        auto maxs = {abs(val - root->val), max_check_value(root->left, val), max_check_value(root->right, val)};
        return *max_element(begin(maxs), end(maxs));
    }

public:
    int maxAncestorDiff(TreeNode* root)
    {
        if(!root)
            return 0;
        auto maxs =
        {
            max_check_value(root->left, root->val),
            max_check_value(root->right, root->val),
            maxAncestorDiff(root->right),
            maxAncestorDiff(root->left)
        };

        return *max_element(begin(maxs), end(maxs));
    }
};