二叉树中和为某一值的路径

import java.util.ArrayList;
/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;
    }
}
*/
public class Solution {
    private ArrayList<ArrayList<Integer>> res=new ArrayList<ArrayList<Integer>>();
    private ArrayList<Integer> path=new ArrayList<Integer>();
    public ArrayList<ArrayList<Integer>> FindPath(TreeNode root,int target) {
        if(root==null){
            return res;
        }
        path.add(root.val);
        if(root.val==target&&root.left==null&&root.right==null){
            res.add(new ArrayList<Integer>(path));
        }
        FindPath(root.left,target-root.val);
        FindPath(root.right,target-root.val);
        path.remove(path.size()-1);
        return res;
    }
}