Today I have done leetcode's December LeetCoding Challenge with cpp.

December LeetCoding Challenge 9

Description

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

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  int maxAncestorDiff(TreeNode* root, int mmin = INT_MAX, int mmax = INT_MIN) {
    // root node will not be nullptr by constraints
    if(!root) return mmax - mmin;
    mmin = min(mmin, root->val);
    mmax = max(mmax, root->val);
    return max(maxAncestorDiff(root->left, mmin, mmax), maxAncestorDiff(root->right, mmin, mmax));
  }
};

// Accepted
// 28/28 cases passed (3 ms)
// Your runtime beats 97.1 % of cpp submissions
// Your memory usage beats 97.32 % of cpp submissions (9.7 MB)