8.Maximum Depth of Binary Tree

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int maxDepth(TreeNode* root) {
            if(root==NULL)return 0;
            if(root->left!=NULL&&root->right!=NULL)
                return max(maxDepth(root->left)+1,maxDepth(root->right)+1);
            else if(root->left==NULL&&root->right!=NULL) return maxDepth(root->right)+1;
            else if(root->right==NULL&&root->left!=NULL) return maxDepth(root->left)+1;
            else return 1;
    }
};