【树】1022. 从根到叶的二进制数之和

 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     int sum; // 全局变量哈
13     int sumRootToLeaf(TreeNode* root)
14     {
15         sum = 0;
16         dfs(root,0);
17         return sum;
18     }
19 
20     void dfs( TreeNode* root, int n)
21     {
22         if(root == NULL)
23         {
24             return;
25         }
26         
27         int val = (n<<1) | root->val;
28 
29         if(root->left==NULL && root->right==NULL)
30         {
31             sum += val; 
32         }
33         else
34         {
35             dfs(root->left,val);
36             dfs(root->right,val);
37         }
38     }
39 };