1026.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
  // Runtime: 8 ms, faster than 92.53% of C++ online submissions for Maximum
  // Difference Between Node and Ancestor.
public:
  int maxAncestorDiff(TreeNode *root) {
    int ret = 0;
    function<void(TreeNode *, int, int)> recursion =
        [&ret, &recursion](auto root, auto maxVal, auto minVal) {
          ret = max({abs(maxVal - root->val), abs(minVal - root->val), ret});
          maxVal = max(root->val, maxVal);
          minVal = min(root->val, minVal);
          if (root->left)
            recursion(root->left, maxVal, minVal);
          if (root->right)
            recursion(root->right, maxVal, minVal);
        };
    recursion(root, root->val, root->val);
    return ret;
  }
};