Input: The root of a Binary Search Tree like this:
              5
            /   \
           2     13
Output: The root of a Greater Tree like this:
             18
            /   \
          20     13

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    private int sum = 0;
    public TreeNode convertBST(TreeNode root) {
        if (root != null) {
            convertBST(root.right);
            sum += root.val;
            root.val = sum;
            convertBST(root.left);
        }
        return root;
    }
}

package common;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
public class TreeNode {
    public int val;
    public TreeNode left;
    public TreeNode right;
    public TreeNode() { }
    public TreeNode(int val) {
        this.val = val;
    }
    public TreeNode(int val, TreeNode left, TreeNode right) {
          this.val = val;
          this.left = left;
          this.right = right;
    }
    @Override
    public String toString() {
        if (this == null) {
            return "null";
        }
        String result = "";
        List<String> row = null;
        List<List<String>> list = new ArrayList<List<String>>();
        LinkedList<TreeNode> rowNode = new LinkedList<>();
        rowNode.add(this);
        while (!rowNode.isEmpty()) {
            int rowSize = rowNode.size();
            row = new ArrayList<String>();
            int rowCount = rowSize;
            int nullCount = 0;
            while (rowSize > 0) {
                TreeNode current = rowNode.pop();
                if (current == null) {
                    row.add("null");
                    nullCount++;
                } else {
                    row.add(Integer.toString(current.val));
                }
                if (current == null || current.left == null) {
                    rowNode.add(null);
                } else {
                    rowNode.add(current.left);
                }
                if (current == null || current.right == null) {
                    rowNode.add(null);
                } else {
                    rowNode.add(current.right);
                }
                rowSize--;
            }
            if (nullCount == rowCount) {
                break;
            }
            list.add(row);
        }
        // print data
        String blank = "    ";
        for (int i = 0; i < list.size(); i ++) {
            for (int j = i; j < list.size(); j++) {
                // print blank
                System.out.print(blank);
            }
            List<String> rowList = list.get(i);
            for (int k = 0; k < rowList.size(); k++) {
                System.out.print(rowList.get(k));
                System.out.print(blank);
            }
            System.out.println();
        }
        //return Arrays.toString(list.toArray());
        return super.toString();
    }
}

public static void main(String[] args) {
    //TreeNode left1 = new TreeNode(2);
    //TreeNode right1 = new TreeNode(13);
    //
    //TreeNode root = new TreeNode(5, left1, right1);
    TreeNode left1 = new TreeNode(1);
    TreeNode right1 = new TreeNode(3);
    TreeNode rootLeft = new TreeNode(2, left1, right1);
    TreeNode left2 = new TreeNode(6);
    TreeNode right2 = new TreeNode(15);
    TreeNode rootRight = new TreeNode(13, left2, right2);
    TreeNode root = new TreeNode(5, rootLeft, rootRight);
    root.toString();
  // 当前类的名字
    ConvertBSTToGreaterTree obj = new ConvertBSTToGreaterTree();
    TreeNode result = obj.convertBST(root);
    result.toString();
  }

            5    
        2    13    
    1    3    6    15    
            39    
        44    28    
    45    42    34    15    

unzip /path/to/ngrok.zip

$ cd $home
$ vim .zshrc
// 添加如下 信息 到环境变量
# ngrok
export NGROK_HOME="/Users/yourpath/software/ngrok"
export PATH=$NGROK_HOME:$PATH
// esc > :wq 保存
// 重新加载 配置文件
source .zshrc

ngrok
NAME:
   ngrok - tunnel local ports to public URLs and inspect traffic
DESCRIPTION:
    ngrok exposes local networked services behinds NATs and firewalls to the
    public internet over a secure tunnel. Share local websites, build/test
    webhook consumers and self-host personal services.
    Detailed help for each command is available with 'ngrok help <command>'.
    Open http://localhost:4040 for ngrok's web interface to inspect traffic.
EXAMPLES:
    ngrok http 80                    # secure public URL for port 80 web server
    ngrok http -subdomain=baz 8080   # port 8080 available at baz.ngrok.io
    ngrok http foo.dev:80            # tunnel to host:port instead of localhost
    ngrok http https://localhost     # expose a local https server
    ngrok tcp 22                     # tunnel arbitrary TCP traffic to port 22
    ngrok tls -hostname=foo.com 443  # TLS traffic for foo.com to port 443
    ngrok start foo bar baz          # start tunnels from the configuration file
VERSION:
   2.3.35
AUTHOR:
  inconshreveable - <alan@ngrok.com>
COMMANDS:
   authtoken	save authtoken to configuration file
   credits	prints author and licensing information
   http		start an HTTP tunnel
   start	start tunnels by name from the configuration file
   tcp		start a TCP tunnel
   tls		start a TLS tunnel
   update	update ngrok to the latest version
   version	print the version string
   help		Shows a list of commands or help for one command

./ngrok authtoken 1cz..yourtoken.X6

ngrok http 8080