C++/代码：

C++/代码：

class Solution {
public:
        vector<vector<int>> Print(TreeNode* pRoot) {
            vector<vector<int>> res; //定义二维输出数组
            if (!pRoot) return res;
            queue<TreeNode*> q;
            q.push(pRoot);
            q.push(NULL); //插入结束标识符
            vector<int> level;
            while (q.size()) {
                auto t = q.front();
                q.pop();
                if (!t) {
                    if (level.empty()) break;
                    res.push_back(level);
                    level.clear();
                    q.push(NULL); //插入结束标识符
                    continue;
                }
                level.push_back(t->val);
                if (t->left) q.push(t->left);
                if (t->right) q.push(t->right);
            }
            return res;
        }
};