include

class Solution {
public:
vector<int> PrintFromTopToBottom(TreeNode* root) {
vector<int> res;
queue<TreeNode*> que;</int></int>

    if(root)
        que.push(root); //首先根结点进去

    while(!que.empty())
    { 
        TreeNode *temp = que.front();
        que.pop();
        res.push_back(temp->val);
        if(temp->left)
            que.push(temp->left);
        if(temp -> right)
            que.push(temp->right);
    }
    return res;