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         vector<int> vv;
14         if (root == NULL)
15             return vv;
16         std::queue<TreeNode *> qq;
17         qq.push(root);
18         TreeNode *tem;
19         while(!qq.empty())
20         {
21             tem = qq.front();
22             qq.pop();
23             vv.push_back(tem->val);
24             if (tem ->left != NULL)
25                 qq.push(tem->left);
26             if(tem ->right != NULL)
27                 qq.push(tem->right);
28         }
29         return vv;
30     }
31 };