二叉树中和为某一值的路径（递归&回溯）

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/
class Solution {
public:
    vector<vector<int> > FindPath(TreeNode* root,int expectNumber) {
        if(root==NULL)
        {
            return ans;
        }
        tmp.push_back(root->val);
        if((root->val==expectNumber)&&(root->left==NULL)&&(root->right==NULL))
        {
            ans.push_back(tmp);
        }
        FindPath(root->left,expectNumber-root->val);
        FindPath(root->right,expectNumber-root->val);
        if(tmp.size()!=0)
        {
            tmp.pop_back();//回溯
        }
        return ans;
    }
private:
       vector<vector<int>> ans;
       vector<int> tmp ;
};