leetcode日记（91）二叉树的最大深度

好久没看到过这么纯粹的简单题了……

递归就行了。

/**
 * Definition for a binary tree node.
 * 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==NULL) return 0;
        else if(root->left&&root->right) return max(maxDepth(root->left),maxDepth(root->right))+1;
        else if(root->left) return maxDepth(root->left)+1;
        else if(root->right) return maxDepth(root->right)+1;
        else return 1;
        return 1;
    }
};