[LeetCode] Binary Tree Zigzag Level Order Traversal

class Solution {public:    vector<vector<int> >result;    vector<vector<int> > zigzagLevelOrder(TreeNode *root) {        vector<int> v;        vector<TreeNode*> node;        if(root == NULL)            return result;        node.push_back(root);        int begin = 0,end;        int cnt = 0;        while(begin < node.size()){            end = node.size();            v.clear();            while(begin < end){                TreeNode * root = node[begin];                v.push_back(root -> val);                if(root -> left != NULL)                    node.push_back(root -> left);                if(root -> right != NULL)                    node.push_back(root -> right);                begin ++;            }            if(cnt%2 == 1){                reverse(v.begin(),v.end());            }            result.push_back(v);            cnt ++;        }        return result;    }};