leetcode 103. Binary Tree Zigzag Level Order Traversal

Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and alternate between).

For example:
Given binary tree {3,9,20,#,#,15,7},

    3   / \  9  20    /  \   15   7

return its zigzag level order traversal as:

[  [3],  [20,9],  [15,7]]

class Solution {public:vector<vector<int>> zigzagLevelOrder(TreeNode* root) {vector<vector<int>>re;if (root == NULL)return re;vector<TreeNode*>que;que.push_back(root);vector<int>aa; aa.push_back(root->val); re.push_back(aa);bool left2right = false;while (!que.empty()){vector<TreeNode*>newque;for (int i = 0; i < que.size(); i++){if (que[i]->left != NULL)newque.push_back(que[i]->left);if (que[i]->right != NULL)newque.push_back(que[i]->right);}if (left2right){if (!newque.empty()){vector<int>bb;for (int i = 0; i < newque.size(); i++)bb.push_back(newque[i]->val);re.push_back(bb);}}else{if (!newque.empty()){vector<int>bb;for (int i = newque.size()-1; i >=0; i--)bb.push_back(newque[i]->val);re.push_back(bb);}}left2right = !left2right;que = newque;}return re;}};