【树】606. 根据二叉树创建字符串

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12      string tree2str(TreeNode *root) 
13      {
14         if(root == NULL)
15             return "";
16 
17         std::string str = std::to_string(root->val);
18 
19         if(root->left == NULL && root->right == NULL)
20             return str + "";
21  
22         if(root->right == NULL)
23             return str + "("+tree2str(root->left)+")";
24 
25         return str + "("+tree2str(root->left)+")("+tree2str(root->right)+")";   
26     }
27 };