给定值，寻找二叉树中满足的所有路径

 import java.util.ArrayList;
 class TreeNode {
      int val;
      TreeNode left;
      TreeNode right;
      TreeNode(int x) { val = x; }
  }

public class Solution {

    ArrayList<ArrayList<Integer>> arr=new ArrayList<ArrayList<Integer>>();
    public ArrayList<ArrayList<Integer>> pathSum(TreeNode root, int sum) {
        ArrayList<Integer>list=new ArrayList<>();

          getPaths(root,sum,list);
          return arr;
    }

    //递归函数实现路径存储
    public void getPaths(TreeNode root,int sum,ArrayList<Integer>list){
         if(root==null) return;
         if(root.left==null&&root.right==null&&sum-root.val==0){

             list.add(root.val);
             arr.add(new ArrayList<Integer>(list));
             list.remove(list.size()-1);
             return;
         }
         list.add(root.val);
         getPaths(root.left,sum-root.val,list);
         getPaths(root.right,sum-root.val,list);
         list.remove(list.size()-1);

    }

    public static void main(String[]args){
        //System.out.println("Hello World!");
    }
}