/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};
*/
class Solution {
public:
    vector<vector<int> > Print(TreeNode* root) {
        vector<vector<int>> res;

        bool even = false;
        if(root==nullptr) return res;

        std::deque<TreeNode*> q;
        if(root!=nullptr){
            q.push_back(root);
        }
        while(!q.empty()){
            vector<int> result;
            int lo=0;int hi=q.size();
            while(lo++<hi){

            TreeNode* node = q.front();
            result.push_back(node->val);
            q.pop_front();
            if(node->left)
                q.push_back(node->left);
            if(node->right)
                q.push_back(node->right);
        }
        if(even){
            std::reverse(result.begin(),result.end());
        }
        even = !even;
        res.push_back(result);
        }
        return res;

    }

};