二叉树中和为某一值的路径

import java.util.ArrayList;
import java.util.Stack;

class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}

public class Solution {
    ArrayList<ArrayList<Integer>> Arraylist=new ArrayList<>();
    ArrayList<Integer>list=new ArrayList<>();
    public ArrayList<ArrayList<Integer>> FindPath(TreeNode root,int target) {
        if(root==null){
             return Arraylist;
        }
        list.add(root.val);
        target-=root.val;
        //找到一条路径则加入路径的集合
        if(target==0&&root.left==null&&root.right==null)
        {
             Arraylist.add(new ArrayList<Integer>(list));
        }

        if(root.left!=null)
        {
            FindPath(root.left,target);
        }
        if(root.right!=null)
        {
            FindPath(root.right,target);
        }
        list.remove(list.size()-1);//删除叶节点,回退
        return Arraylist;
    }

    //二叉树的深度遍历
    public void DFS(TreeNode node)
    {
          if(node==null)
          {
             return ;
          }
          Stack<TreeNode>stack=new Stack<>();

          stack.push(node);
          while(!stack.isEmpty())
          {
            TreeNode tmp=stack.pop();
            System.out.print(tmp.val+" ");

            if(tmp.left!=null)
            {
              DFS(tmp.left);
            }


            if(tmp.right!=null)
            {
              DFS(tmp.right);
            }
          }

    }

    public static void main(String[]args){
        //System.out.println("Hello");
        TreeNode root=new TreeNode(1);
        root.left=new TreeNode(2);
        root.right=new TreeNode(3);
        root.left.left=new TreeNode(4);
        root.left.right=new TreeNode(5);
        root.right.left=new TreeNode(6);
        root.right.right=new TreeNode(7);
        Solution s=new Solution();
        s.FindPath(root,7);
    }
}