104. Maximum Depth of Binary Tree

Given the root of a binary tree, return its maximum depth.

A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Example 1:

Input: root = [3,9,20,null,null,15,7]
Output: 3

Example 2:

Input: root = [1,null,2]
Output: 2

Constraints:

• The number of nodes in the tree is in the range [0, 104].

• -100 <= Node.val <= 100

  class Solution {
  public:
  int maxDepth(TreeNode* root) {
  if(root==nullptr)return 0;
  return max(maxDepth(root->left),maxDepth(root->right))+1;
  }
  };