Day 15 Leet code series, today we will be picking the problem Maximum Depth of Binary Tree (https://leetcode.com/problems/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

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