/**

  * Definition for a binary tree node.

  * struct TreeNode {

  *     int val;

  *     TreeNode *left;

  *     TreeNode *right;

  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

  * };

  */

 class Solution {

 public:

     vector<vector<int> > pathSum(TreeNode* root, int sum) {

         if(root==NULL)  return ans;

         DFS(root,,sum,tmp);

         return ans;

     }

     void DFS(TreeNode* t,int n,const int& sum,vector<int>& num)

     {

         num.push_back(t->val);

         n+=t->val;

         if(t->left==NULL&&t->right==NULL)

         {

             if(n==sum)  ans.push_back(num);

         }

         else

         {

             if(t->left)     DFS(t->left,n,sum,num);

             if(t->right)    DFS(t->right,n,sum,num);

         }

         num.pop_back();

     }

 private:

     vector<vector<int>> ans;

     vector<int> tmp;

 };