/**
 * 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>> res;
    vector<int> aux;
    
   void
 
 pathSum1(TreeNode* root, int sum) 
   {       
       if(root->left == root->right)
       {
           if(sum == root->val)
           {
               aux.push_back(sum);
               res.push_back(aux);
               aux.pop_back();
           }
       }
       
       aux.push_back(root
 
->val);
       if(root->left)
       {
           pathSum1(root->left, sum-root->val);
       }
       
       if(root->right)
       {
           pathSum1(root->right, sum-root->val);
       }
       aux.pop_back();
   }
    
    vector<vector<int>> pathSum(TreeNode* root, int
 
 sum) {
        res.clear();
        if(root==NULL)
            return vector<vector<int>>();
        pathSum1(root, sum);
        return res;
    }
};

Leetcode 113. 路徑總和 II