lintcode-dfs实现二叉树的层序遍历

 class Solution {
     /**
      * @param root: The root of binary tree.
      * @return: Level order a list of lists of integer
      */
     struct node{
         TreeNode* tn;
         int cnt;
         node(TreeNode* tn, int cnt){
                 this->tn = tn;
                 this->cnt = cnt;
         }
     };

 public:
     void dfs(vector<vector<int>> &ans, queue<node*> &que){
             if(que.empty()) return ;
             node* now = que.front();
             que.pop();

             if(now->tn->left) que.push(new node(now->tn->left, now->cnt + ));
             if(now->tn->right) que.push(new node(now->tn->right, now->cnt + ));

             if((int)ans.size() -  < now->cnt){
                 vector<int> v(,now->tn->val);
                 ans.push_back(v);

             } else {
                 ans[now->cnt].push_back(now->tn->val);
             }

             dfs(ans, que);

     }
     vector<vector<int>> levelOrder(TreeNode *root) {
         // write your code here
         vector<vector<int>> ans;
         if(root == NULL) return ans;
         queue<node*> que;
         que.push(new node(root,));
         dfs(ans, que);
         return ans;
     }
 };