[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]
]

将一个数组加入到解之前，根据题目要求调整一下正向或反向的顺序即可。

/**
 * 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> > ans;
        vector<TreeNode*> v;
        vector<TreeNode*> tmp;
        vector<int> array;
        if(root == NULL)
            return ans;
        v.push_back(root);
        int count = 0;
        while(!v.empty())
        {
            array.clear();
            tmp.clear();
            if(count % 2 == 0)
            {
                for(int i = 0;i < v.size();i++)
                {
                    array.push_back(v.at(i)->val);
                }
            }
            else
            {
                for(int i = v.size() - 1; i >= 0; i--)
                {
                    array.push_back(v.at(i)->val);
                }                
            }
            ans.push_back(array);
            for(int j = 0;j<v.size();j++)
            {
                if(v.at(j)->left != NULL)
                    tmp.push_back(v.at(j)->left);
                if(v.at(j)->right != NULL)
                    tmp.push_back(v.at(j)->right);
            }
            v = tmp;
            count++;
        }
        return ans;
    }
};