[leetcode]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]
]

/**
* Definition for binary tree
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<vector<int> > zigzagLevelOrder(TreeNode *root) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
vector<vector<int>> result;
if(!root) return result;

vector<int> tmp;
queue<TreeNode*> q1, q2;
q1.push(root);

TreeNode *cur;

int order = 1;
while(!q1.empty()){
tmp.clear();
while(!q1.empty()){
cur = q1.front();
q1.pop();

tmp.push_back(cur->val);
if(cur -> left) q2.push(cur->left);
if(cur -> right) q2.push(cur->right);
}
if(order == 1){
result.push_back(tmp);
order = 0;
}else{
reverse(tmp.begin(), tmp.end());
result.push_back(tmp);
order = 1;
}

swap(q1, q2);
}

return result;

}
};