Solution.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 {
public:
    int maxAncestorDiff(TreeNode* root) {
        int ans = 0;
        function<void(TreeNode*, int, int)> dfs = [&](TreeNode* root, int mi, int mx) {
            if (!root) {
                return;
            }
            ans = max({ans, abs(mi - root->val), abs(mx - root->val)});
            mi = min(mi, root->val);
            mx = max(mx, root->val);
            dfs(root->left, mi, mx);
            dfs(root->right, mi, mx);
        };
        dfs(root, root->val, root->val);
        return ans;
    }
};