关卡地址

解决方案：

思路：

这一关鼠标移动到图片上指针会变成小手，点击会得到如下信息：

and the next nothing is 44827

同时，url后面多了参数?nothing=12345。回退回关卡地址，查看源代码得到如下提示：

urllib may help. DON’T TRY ALL NOTHINGS, since it will never end. 400 times is more than enough.

结合标题，需要借助urllib库发送400次请求，每次请求都会得到下一次请求的参数，替换参数继续请求，最终得到下一关地址。

PS： 在测试时，遇到这样的提示：Yes. Divide by two and keep going.，已在程序中做判断处理（之前并没有遇到这样的情况，看官方攻略也不像是网站最近更新了，看来是之前比较幸运😝）。

代码：

Challenge004.py

url='http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing='
param='12345'

import urllib.request
import re

pattern=re.compile("the next nothing is (\\d+)")

for i in range(400):
    # print("request %4d url: %s " %(i,url+param))

    resp=urllib.request.urlopen(url+param).read().decode('utf-8')
    try:
        param=pattern.search(resp).group(1)
    except:
        print("param %s, response: %s" %(param,resp))
        if resp == "Yes. Divide by two and keep going.":
            try:
                tmpParam=str(int(int(param)/2))
                param=tmpParam
                continue
            except:
                break
        break

print('completed')
PS src\static> python .\Code\Python\Challenge004.py

Challenge004.ps1

$url="http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing="
$param="12345"

$pattern=[regex]"the next nothing is (\d+)"

for ($i=0; $i -lt 400; $i++) {
    $resp = (Invoke-WebRequest -Uri $url+$param | Select-Object -ExcludeProperty Content).Content
    $match = $pattern.Match($resp)
    if ($match.Success) {
        $param = $match.Groups[1].Value
    } else {
        [System.Console]::WriteLine($("param: {0}, resp: {1}" -f $param,$resp))
        if ($resp -eq "Yes. Divide by two and keep going.") {
            $param=$param/2
            continue
        }
        break
    }
}

[System.Console]::WriteLine("completed")
PS src\static> .\Code\PowerShell\Challenge004.ps1

Challenge004.go

package main

import (
	"fmt"
	"net/http"
	"io/ioutil"
	"regexp"
	"strings"
	"strconv"
)

func (c *Challenge) Challenge004() {
	url:="http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing="
	param:="12345"

	pattern:=regexp.MustCompile("the next nothing is (\\d+)")

	for i:=0; i<400; i++ {
		resp := httpGet(url+param)
		tmpParam:=pattern.FindStringSubmatch(resp)
		if len(tmpParam) != 2 {
			fmt.Printf("param: %s, response: %s\n",param, resp)
			if strings.Compare(resp,"Yes. Divide by two and keep going.") == 0 {
				intParam,err := strconv.Atoi(param)
				if err == nil {
					param = string(intParam/2)
					continue
				}
			}
			break
		} else {
			param=tmpParam[1]
		}
	}

	fmt.Println("completed")
}

func httpGet(url string) string {
	resp, err := http.Get(url)
	if err == nil {
		defer resp.Body.Close()
		body, err := ioutil.ReadAll(resp.Body)
		if err == nil {
			return string(body)
		}
	}
	return ""
}
PS src\static> .\Code\Go\Challenge.exe -l 004

最终结果： peak.html

[下一关地址][5]