TreeNode.cpp

// Maximum depth of binary tree
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
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 maxDepth(TreeNode* root) {
        if(root == nullptr)
            return 0;
        return max(maxDepth(root->left), maxDepth(root->right)) + 1;
    }
};

int main()
{
    Solution s;
    TreeNode *root = new TreeNode(3);
    root->left = new TreeNode(9);
    root->right = new TreeNode(20);
    root->right->left = new TreeNode(15);
    root->right->right = new TreeNode(7);
    int ret = s.maxDepth(root);
    cout << ret << endl;

    return 0;
}

// Definition for a binary tree node.