从上往下打印二叉树

1 struct TreeNode {
2     int val;
3     struct TreeNode *left;
4     struct TreeNode *right;
5     TreeNode(int x) :
6             val(x), left(NULL), right(NULL) {
7     }
8 };

 1 vector<int> PrintFromTopToBottom(TreeNode *root) {
 2     queue<TreeNode*> nodes;
 3     vector<int> outputValue;
 4     if(root == NULL)
 5         return outputValue;
 6     int index = 0;
 7     nodes.push_back(root);
 8     while(!nodes.empty()){
 9         TreeNode* node;
10         node = nodes.front();
11         outputValue.push_back(node->val);
12         if(node->left != NULL)
13             nodes.push(node->left);
14         if(node->right != NULL)
15             nodes.push(node->right);
16     }
17     return outputValue;
18 }