C++：从上到下打印二叉树

class Solution {
public:
vector<int> PrintFromTopToBottom(TreeNode* root) {
vector<int> vec;
if(root == NULL) {
return vec;
}
vector<TreeNode> q;
q.push_back(root);
while(!q.empty()) {
TreeNode node = q.front();
q.erase(q.begin());
vec.push_back(node->val);
if(node->left)q.push_back(node->left);
if(node->right)q.push_back(node->right);
}
return vec;
}
};</int></int>