从上往下打印二叉树

 1 /*
 2 struct TreeNode {
 3     int val;
 4     struct TreeNode *left;
 5     struct TreeNode *right;
 6     TreeNode(int x) :
 7             val(x), left(NULL), right(NULL) {
 8     }
 9 };*/
10 class Solution {
11 public:
12     vector<int> PrintFromTopToBottom(TreeNode *root) {
13         
14         queue<TreeNode *> q;
15         vector<int> res;
16         TreeNode * tmp=NULL;
17         if(root==NULL) return res;
18         q.push(root);
19         while(!q.empty()){
20             tmp=q.front();
21             res.push_back(tmp->val);
22             q.pop();
23             if(tmp->left!=NULL)
24                 q.push(tmp->left);
25             if(tmp->right!=NULL)
26                 q.push(tmp->right);
27         }
28         return res;
29     }
30 };