leetcode-Binary Tree Zigzag Level Order Traversa

/**
 * 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)
    {
        vector<vector<int>> result;
        vector<int> vec;
        result.clear();
        if(NULL==root)
            return result;
        deque<TreeNode*>deq;
        deq.clear();
        deq.push_back(root);
        int len1 = 1;
        int len2 ;
        bool dir = true;
        while(!deq.empty())
        {
            len2 = 0;
            if(dir)
            {
                while(len1--)
                {
                    vec.push_back(deq.front()->val);
                    if(deq.front()->left!=NULL)
                    {
                           deq.push_back(deq.front()->left);
                           len2++;
                    }
                    if(deq.front()->right!=NULL)
                    {
                         deq.push_back(deq.front()->right);
                         len2++;
                    }
                     deq.pop_front();
                }
                dir = !dir;
            }
            else
            {
                while(len1--)
                {
                    vec.push_back(deq.back()->val);
                    if(deq.back()->right!=NULL)
                    {
                         deq.push_front(deq.back()->right);
                         len2++;
                    }
                    if(deq.back()->left!=NULL)
                    {
                           deq.push_front(deq.back()->left);
                           len2++;
                    }
                   
                     deq.pop_back();
                }
                dir = !dir;
            }
            result.push_back(vec);
            len1=len2;
            vec.clear();
        }
        return result;
    }
};

1. 双端队列完成

2. 记住clear()