binary-tree-zigzag-level-order-traversal

题目：

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]
]

程序：

class Solution {public:    vector<vector<int> > zigzagLevelOrder(TreeNode *root) {        vector<vector<int>> result;        queue<TreeNode *> q;        if(root != NULL)            q.push(root);        while(!q.empty())        {            int n = q.size();            vector<int> v;            while(n--)            {                TreeNode *p = q.front();                q.pop();                if(p->left)                    q.push(p->left);                if(p->right)                    q.push(p->right);                v.push_back(p->val);            }            if(result.size()%2 != 0)                reverse(v.begin(), v.end());            result.push_back(v);        }        return result;    }};