Maximum Depth of Binary Tree

//104
Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

class Solution {
public:
    int maxDepth(TreeNode* root) {
        if(root==NULL){
            return 0;
        }

        int leftTree=maxDepth(root->left);
        int rightTree=maxDepth(root->right);

        return max(leftTree,rightTree)+1;
    }
};