LeetCode Path Sum II （DFS）

/**
* 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,0,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;
};