how to make a function from using global var to not using it

let say, we want to find the bottom left node in a tree.
one way to do it is using global vars:

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution
{

    public int findBottomLeftValue(TreeNode root)
    {
        find(root, 0);
        return d_bottomLeft.val;
    }

    private int d_bottomDepth = -1;
    private TreeNode d_bottomLeft = null;
    private void find(TreeNode node, int depth)
    {
        if (node == null) return;
        if (depth >= d_bottomDepth)
        {
            d_bottomDepth = depth;
            d_bottomLeft = node;
        }

        find(node.right, depth + 1);
        find(node.left , depth + 1);
    }
}

to avoid using global vars, we can write it in this way:

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution
{
    public int findBottomLeftValue(TreeNode root)
    {
        Result result = new Result();
        find(root, 0, result);
        return result.d_bottomLeft.val;
    }

    private void find(TreeNode node, int depth, Result result)
    {
        if (node == null) return;
        if (depth >= result.d_bottomDepth)
        {
            result.d_bottomDepth = depth;
            result.d_bottomLeft = node;
        }
        find(node.right, depth + 1, result);
        find(node.left , depth + 1, result);
    }

    private class Result
    {
        public int d_bottomDepth = -1;
        public TreeNode d_bottomLeft = null;
    }
}