Rosetta Code/Tasks without examples

From Rosetta Code
Rosetta Code/Tasks without examples is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
A RosettaCode contributor is going on a long journey. To ease the boredom of a long flight he takes his favourite programming language manual and a list of RosettaCode tasks, but there's a catch: the tasks have to be description only and not include all the solutions already supplied by other programmers.

Task: Scrape http://rosettacode.org/wiki/Category:Programming_Tasks for all the tasks. Traverse the links. Extract the text or html between a tag with a class of "infobox" and the beginning of the table with the id of "toc".

Go[edit]

package main
 
import (
"fmt"
"html"
"io/ioutil"
"net/http"
"regexp"
"strings"
"time"
)
 
func main() {
ex := `<li><a href="/wiki/(.*?)"`
re := regexp.MustCompile(ex)
page := "http://rosettacode.org/wiki/Category:Programming_Tasks"
resp, _ := http.Get(page)
body, _ := ioutil.ReadAll(resp.Body)
matches := re.FindAllStringSubmatch(string(body), -1)
resp.Body.Close()
tasks := make([]string, len(matches))
for i, match := range matches {
tasks[i] = match[1]
}
const base = "http://rosettacode.org/wiki/"
const limit = 3 // number of tasks to print out
ex = `(?s)using any language you may know.</div>(.*?)<div id="toc"`
ex2 := `</?[^>]*>` // to remove all tags including links
re = regexp.MustCompile(ex)
re2 := regexp.MustCompile(ex2)
for i, task := range tasks {
page = base + task
resp, _ = http.Get(page)
body, _ = ioutil.ReadAll(resp.Body)
match := re.FindStringSubmatch(string(body))
resp.Body.Close()
text := html.UnescapeString(re2.ReplaceAllLiteralString(match[1], ""))
fmt.Println(strings.Replace(task, "_", " ", -1), "\n", text)
if i == limit-1 {
break
}
time.Sleep(5 * time.Second) // wait 5 seconds before processing next task
}
}
Output:

Text rather than HTML:

100 doors 
 
There are 100 doors in a row that are all initially closed.
You make 100 passes by the doors.
The first time through, visit every door and  toggle  the door  (if the door is closed,  open it;   if it is open,  close it).
The second time, only visit every 2nd door   (door #2, #4, #6, ...),   and toggle it.
The third time, visit every 3rd door   (door #3, #6, #9, ...), etc,   until you only visit the 100th door.


Task

Answer the question:   what state are the doors in after the last pass?   Which are open, which are closed?

Alternate:
As noted in this page's   discussion page,   the only doors that remain open are those whose numbers are perfect squares.
Opening only those doors is an   optimization   that may also be expressed;
however, as should be obvious, this defeats the intent of comparing implementations across programming languages.



15 Puzzle Game 
 
 


Task

Implement the Fifteen Puzzle Game.

The   15-puzzle   is also known as:

   Fifteen Puzzle
   Gem Puzzle
   Boss Puzzle
   Game of Fifteen
   Mystic Square
   14-15 Puzzle
   and many others.


Related Tasks

   15 Puzzle Solver
   16 Puzzle Game



15 puzzle solver 
 
Your task is to write a program that finds a solution in the fewest moves possible single moves to a random Fifteen Puzzle Game.
For this task you will be using the following puzzle:

15 14  1  6
 9 11  4 12
 0 10  7  3
13  8  5  2


Solution: 1  2  3  4
 5  6  7  8
 9 10 11 12
13 14 15  0

The output must show the moves' directions, like so: left, left, left, down, right... and so on.
There are two solutions, of fifty-two moves:
rrrulddluuuldrurdddrullulurrrddldluurddlulurruldrdrd
rrruldluuldrurdddluulurrrdlddruldluurddlulurruldrrdd
see: Pretty Print of Optimal Solution
Finding either one, or both is an acceptable result.

Extra credit.
Solve the following problem:

  0 12  9 13
 15 11 10 14
  3  7  2  5
  4  8  6  1



Related Task

 15 puzzle game
 A* search algorithm

Perl[edit]

Slice and dice the HTML. Output is as for the other examples.

use strict;
use warnings;
 
use LWP::UserAgent;
my $ua = LWP::UserAgent->new;
 
# get list of task titles
my $html = $ua->request( HTTP::Request->new( GET => 'http://rosettacode.org/wiki/Category:Programming_Tasks'))->content;
my @tasks = $html =~ m#<li><a href="/wiki/(.*?)"#g;
 
# download tasks, and extract task descriptions
for my $title (@tasks) {
my $html = $ua->request( HTTP::Request->new( GET => "http://rosettacode.org/wiki/$title" ))->content;
my($task_at_hand) = $html =~ m#using any language you may know.</div>(.*?)<div id="toc"#s;
print "$title\n$task_at_hand\n\n";
sleep 10; # so you have time to read each task...
}

Perl 6[edit]

Works with: Rakudo version 2017.10
use HTTP::UserAgent;
use Gumbo;
 
my $ua = HTTP::UserAgent.new;
my $taskfile = './RC_tasks.html';
 
# Get list of Tasks
say "Updating Programming_Tasks list...";
my $page = "http://rosettacode.org/wiki/Category:Programming_Tasks";
my $html = $ua.get($page).content;
my $xmldoc = parse-html($html, :TAG<div>, :id<mw-pages>);
my @tasks = parse-html($xmldoc[0].Str, :TAG<li>).Str.comb( /'/wiki/' <-["]>+ / )».substr(6); #"
my $f = open("./RC_Programming_Tasks.txt", :w) or die "$!\n";
note "Writing Programming_Tasks file...";
$f.print( @tasks.join("\n") );
$f.close;
 
sleep .5;
 
for 'Programming_Tasks' -> $category
{ # Scrape info from each page.
 
note "Loading $category file...";
note "Retreiving tasks...";
my @entries = "./RC_{$category}.txt".IO.slurp.lines;
 
for @entries -> $title {
note $title;
 
# Get the raw page
my $html = $ua.get: "http://rosettacode.org/wiki/{$title}";
 
# Filter out the actual task description
$html.content ~~ m|'<div id="mw-content-text" lang="en" dir="ltr" class="mw-content-ltr"><div'
.+? 'using any language you may know.</div>' (.+?) '<div id="toc"'|;
 
my $task = cleanup $0.Str;
 
# save to a file
my $fh = $taskfile.IO.open :a;
 
$fh.put: "<hr>\n $title\n<hr>\n$task";
 
$fh.close;
 
sleep 3; # Don't pound the server
}
}
 
sub cleanup ( $string ) {
$string.subst( /^.+ '</div>'/, '' )
}
Abridged sample output:

    100_doors

There are 100 doors in a row that are all initially closed.

You make 100 <a href="/wiki/Rosetta_Code:Multiple_passes" title="Rosetta Code:Multiple passes">passes</a> by the doors.

The first time through, visit every door and  toggle  the door  (if the door is closed,  open it;   if it is open,  close it).

The second time, only visit every 2nd door   (door #2, #4, #6, ...),   and toggle it.

The third time, visit every 3rd door   (door #3, #6, #9, ...), etc,   until you only visit the 100th door.


Task

Answer the question:   what state are the doors in after the last pass?   Which are open, which are closed?


<a href="/wiki/Rosetta_Code:Extra_credit" title="Rosetta Code:Extra credit">Alternate</a>: As noted in this page's   <a href="/wiki/Talk:100_doors" title="Talk:100 doors">discussion page</a>,   the only doors that remain open are those whose numbers are perfect squares.

Opening only those doors is an   <a href="/wiki/Rosetta_Code:Optimization" title="Rosetta Code:Optimization">optimization</a>   that may also be expressed;

however, as should be obvious, this defeats the intent of comparing implementations across programming languages.


    15_Puzzle_Game

Task

Implement the <a href="http://en.wikipedia.org/wiki/15_puzzle" class="extiw" title="wp:15 puzzle">Fifteen Puzzle Game</a>.

Related Task
  • <a href="/wiki/15_puzzle_solver" title="15 puzzle solver">15 Puzzle Solver</a>




    15_puzzle_solver

Your task is to write a program that finds a solution in the fewest single moves (no multimoves) possible to a random <a href="http://en.wikipedia.org/wiki/15_puzzle" class="extiw" title="wp:15 puzzle">Fifteen Puzzle Game</a>.
For this task you will be using the following puzzle:

15 14  1  6
 9 11  4 12
 0 10  7  3
13  8  5  2


Solution:
 1  2  3  4
 5  6  7  8
 9 10 11 12
13 14 15  0

The output must show the moves' directions, like so: left, left, left, down, right... and so on.
There are 2 solutions with 52 moves:
rrrulddluuuldrurdddrullulurrrddldluurddlulurruldrdrd
rrruldluuldrurdddluulurrrdlddruldluurddlulurruldrrdd
finding either one, or both is an acceptable result.
see: <a rel="nofollow" class="external text" href="http://www.rosettacode.org/wiki/15_puzzle_solver/Optimal_solution">Pretty Print of Optimal Solution</a>

Extra credit.

Solve the following problem:

  0 12  9 13
 15 11 10 14
  3  7  2  5
  4  8  6  1


Related Task
  • <a href="/wiki/15_Puzzle_Game" title="15 Puzzle Game">15 puzzle game</a>



...and so on...


Phix[edit]

Since downloading all the pages can be very slow, this uses a cache. Limiting by "Phix" fairly obviously speeds it up tenfold :-)
Output similar to zkl, I assume the first four constants are self-explanatory.

-- demo\rosetta\Tasks_without_examples.exw
constant output_html = true,
include_drafts = true,
summary = false,
notlang = "Phix" -- "" for all
 
include builtins\timedate.e
integer refresh_cache = timedelta(days:=30) -- 0 for always
 
include builtins\libcurl.e
atom curl = NULL
atom pErrorBuffer
 
function write_callback(atom pData, integer size, integer nmemb, integer fn)
integer bytes_written = size * nmemb
puts(fn,peek({pData,bytes_written}))
return bytes_written
end function
constant write_cb = call_back({'+', routine_id("write_callback")})
 
function open_download(string filename, url)
bool refetch = true
if get_file_type("rc_cache")!=FILETYPE_DIRECTORY then
if not create_directory("rc_cache") then
crash("cannot create rc_cache directory")
end if
end if
filename = join_path({"rc_cache",filename})
if file_exists(filename) then
-- use existing file if <= refresh_cache (30+ days) old
sequence last_mod = get_file_date(filename) -- (0.8.1+)
atom delta = timedate_diff(last_mod,date())
refetch = (delta>refresh_cache)
else
string directory = get_file_path(filename)
if get_file_type(directory)!=FILETYPE_DIRECTORY then
if not create_directory(directory,make_parent:=true) then
crash("cannot create %s directory",{directory})
end if
end if
end if
if refetch then
printf(1,"Downloading %s...\n",{filename})
if curl=NULL then
curl_global_init()
curl = curl_easy_init()
pErrorBuffer = allocate(CURL_ERROR_SIZE)
curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, pErrorBuffer)
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_cb)
end if
url = substitute(url,"%3A",":")
url = substitute(url,"%2A","*")
curl_easy_setopt(curl, CURLOPT_URL, url)
integer fn = open(filename,"wb")
if fn=-1 then ?9/0 end if
curl_easy_setopt(curl, CURLOPT_WRITEDATA, fn)
CURLcode res = curl_easy_perform(curl)
if res!=CURLE_OK then
string error = sprintf("%d",res)
if res=CURLE_COULDNT_RESOLVE_HOST then
error &= " [CURLE_COULDNT_RESOLVE_HOST]"
end if
printf(1, "Error %s downloading file\n", error)
{} = wait_key()
abort(0)
end if
close(fn)
refresh_cache += timedelta(days:=1) -- did I mention it is slow?
end if
return get_text(filename)
end function
 
function open_category(string filename)
return open_download(filename&".htm","http://rosettacode.org/wiki/Category:"&filename)
end function
 
function dewiki(string s)
sequence tasks = {}
integer start = 1, finish = match(`<div class="printfooter">`,s)
s = s[1..finish-1]
while true do
start = match("<li><a href=\"/wiki/",s,start)
if start=0 then exit end if
start += length("<li><a href=\"/wiki/")
finish = find('"',s,start)
string task = s[start..finish-1]
task = substitute(task,"*","%2A")
task = substitute(task,":","%3A")
tasks = append(tasks,task)
start = finish+1
end while
return tasks
end function
 
function extract_tasks()
-- extract tasks from eg `<li><a href="/wiki/100_doors"`
sequence tasks = dewiki(open_category("Programming_Tasks"))
if include_drafts then
tasks &= dewiki(open_category("Draft_Programming_Tasks"))
end if
if length(notlang) then
-- filter already done in specified language
string langurl = "http://rosettacode.org/wiki/Category:"&notlang
sequence done = dewiki(open_download(notlang&".htm",langurl))
integer k = 0
for i=1 to length(tasks) do
if not find(tasks[i],done) then
k += 1
tasks[k] = tasks[i]
end if
end for
tasks = tasks[1..k]
done = {}
end if
if not summary then
-- replace with contents
for i=1 to length(tasks) do
string ti = tasks[i],
url = sprintf("http://rosettacode.org/wiki/%s",{ti}),
contents = open_download(ti&".htm",url)
integer start = match(`</div>`,contents,match(`<div class="infobox"`,contents))+length(`</div>`)
integer finish = match(`<div id="toc"`,contents,start)-1
-- ... but draft tasks with too few languages have no toc:
if finish=-1 then finish = match(`<h2>`,contents,start)-1 end if
-- ... and if no languages at all, use the footer:
if finish=-1 then finish = match(`</div><div class="printfooter">`,contents,start)-1 end if
if finish=-1 then ?9/0 end if
contents = contents[start..finish]
ti = substitute(ti,"_"," ")
if not match("<b>"&ti&"</b>",contents) then
-- (ps: I refuse to panic over the occasional replicated header...)
contents = sprintf("<h3>%s</h3>%s",{ti,contents})
end if
tasks[i] = contents
if get_key()=#1B then exit end if
end for
end if
if curl!=NULL then
curl_easy_cleanup(curl)
free(pErrorBuffer)
curl = NULL
pErrorBuffer = NULL
end if
return tasks
end function
 
function html_clean(string ri)
ri = substitute(ri,"%3A",":")
ri = substitute(ri,"%E2%80%93","-")
ri = substitute(ri,"%E2%80%99","'")
ri = substitute(ri,"%27","'")
ri = substitute(ri,"%2B","+")
ri = substitute(ri,"%C3%A8","e")
ri = substitute(ri,"%C3%A9","e")
ri = substitute(ri,"%22","\"")
ri = substitute(ri,"%2A","*")
return ri
end function
 
constant html_header = """
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Rosettacode Tasks without examples</title>
</head>
<body>
<h2>Rosettacode Tasks without examples</h2>
Generated %s, %d entries<br><br>
""",
html_footer = """
</body>
</html>
"""
 
sequence results = extract_tasks()
if output_html then
integer fn = open("Tasks_Without_Examples.html","w")
printf(fn,html_header,{format_timedate(date()),length(results)})
for i=1 to length(results) do
printf(fn,"%s<br>",html_clean(results[i]))
end for
puts(fn,html_footer)
close(fn)
else
for i=1 to length(results) do
printf(1,"%s\n",html_clean(results[i]))
end for
end if
 
?"done"
{} = wait_key()

VBScript[edit]

Uses Internet Explorer (v9 and above) to traverse the DOM in the list page and subsequent task pages. Echoes title and href to the console. Outputs files containing html.

Could output text by retrieving innerText instead of innerHTML in Slurp().

Option Explicit
 
Dim oIE : Set oIE = CreateObject("InternetExplorer.Application")
 
Dim oFSO : Set oFSO = CreateObject("Scripting.FileSystemObject")
 
Dim oRE : Set oRE = New RegExp
oRE.Pattern = "class=[" & Chr(34) & "'](.*?)[" & Chr(34) & "']"
oRE.IgnoreCase = True
 
oIE.Navigate "http://rosettacode.org/wiki/Category:Programming_Tasks"
While oIE.Busy
WScript.Sleep 100
Wend
 
Dim oDoc : Set oDoc = oIE.Document
Dim oDict : Set oDict = CreateObject("Scripting.Dictionary")
 
' build a dictionary of anchors
Dim oAnchor
Dim oAnchors : Set oAnchors = oDoc.getElementById("mw-pages").getElementsByTagName("a")
For Each oAnchor In oAnchors
oDict.Add oAnchor.innerText, oAnchor.href
Next
 
'traverse the dictionary of anchors
Dim aKeys : aKeys = oDict.Keys()
Dim aKey
For Each aKey In aKeys
Slurp aKey, oDict(aKey)
Next
 
oIE.Quit
 
Function Slurp(sTitle, sHref)
WScript.Echo sTitle, sHref
 
oIE.Navigate sHref
While oIE.Busy
WScript.Sleep 100
Wend
 
Dim oDoc : Set oDoc = oIE.Document
 
Dim oStart : Set oStart = oDoc.getElementsByClassName("infobox")(0)
Dim oCursor : Set oCursor = oStart
Dim sDescription : sDescription = vbNullString
Dim oThere
Dim iErr
 
Do While oCursor.tagName <> "TABLE" And oCursor.id <> "toc"
Set oThere = oCursor
sDescription = sDescription & oThere.innerHTML & vbNewLine
On Error Resume Next
Set oCursor = oCursor.nextElementSibling
iErr = Err.Number
On Error Goto 0
If iErr <> 0 Then
Exit Do
End If
Loop
 
dim sTitle2
sTitle2 = Replace(sTitle,"/","_")
sTitle2 = Replace(sTitle2,Chr(34),"'")
sTitle2 = Replace(sTitle2,"*",".")
 
Dim oHandle : Set oHandle = oFSO.CreateTextFile(sTitle2 & ".htm", True, True)
oHandle.Write "<a href='" & sHref & "'>" & sTitle & "</a><br><br>"
oHandle.Write sDescription
oHandle.Close
 
oIE.Stop
 
End Function
 

zkl[edit]

This is a bit of a twist on the task: Programmer wants to know which tasks have not been implimeted by their favorite language.

Uses libraries cURL and YAJL (yet another json library).

var [const] CURL=Import("zklCurl"), YAJL=Import("zklYAJL")[0];
 
fcn getTasks(language){
continueValue,tasks,curl := "",Data(0,String), CURL(); // "nm\0nm\0...."
do{ // eg 5 times
page:=curl.get(("http://rosettacode.org/mw/api.php?"
"action=query&cmlimit=500"
"&format=json"
"&list=categorymembers"
"&cmtitle=Category:%s"
"&cmcontinue=%s").fmt(language,continueValue),Void);
page=page[0]; // get HTML body
json:=YAJL().write(page).close();
json["query"]["categorymembers"].pump(tasks,T("get","title"));
continueValue=json.find("continue") #{continue : -||,cmcontinue:page|954|19)}
.toList() # ( ("continue","-||"), ("cmcontinue","page|954|19") )
.apply("concat","=").concat("&"); # continue=-||&cmcontinue=page|954|19
}while(continueValue);
tasks
}
 
var allTasks =getTasks.future("Programming_Tasks"); // thread
var draftTasks=getTasks.future("Draft_Programming_Tasks"); // thread
var tasks =getTasks.future(lang); // thread
 
fcn newTasks{
langTasks:=tasks.pump(Dictionary().add.fp1(Void)); // { "Semordnilap":Void }
unimplementedTasks:=allTasks.filter('!(langTasks.holds))
.extend(draftTasks.filter('!(langTasks.holds)));
#if 0
unimplementedTasks.pump(List()).sort().pump(Console.println);
#else // this next part is very very slow, useless, can't find a wikimedia api
// and the amount of information is pretty overwhelming
curl:=CURL();
foreach task in (unimplementedTasks.pump(List()).sort()){
// some task names have a / in them, can't url encode: "Active Directory/Connect"
page:="https://rosettacode.org/wiki/" + task.replace(" ","_");
page:=curl.get(page)[0]; // sloooow
s,s := page.find("\"infobox\""), page.find("<p>",s);
if(not (e:=page.find("<div id=\"toc\"",s))) e:=page.find("</p>",s);
println("<h2>%s</h2>\n%s\n<hr>".fmt(task,page[s,e-s].text));
}
#endif
}
 
newTasks();
Concise Output:
$ zkl rs_tasks_without.zkl 
15 Puzzle Game
15 puzzle solver
2048
ASCII art diagram converter
AVL tree
Ackermann function
...
Verbose Output:

15 Puzzle Game

Implement the <a href="http://en.wikipedia.org/wiki/15_puzzle" class="extiw" title="wp:15 puzzle">Fifteen Puzzle Game</a>.

Related Task
  • <a href="/wiki/15_puzzle_solver" title="15 puzzle solver">15 Puzzle Solver</a>




15 puzzle solver

Your task is to write a program that finds a solution in the fewest moves possible single moves to a random <a href="http://en.wikipedia.org/wiki/15_puzzle" class="extiw" title="wp:15 puzzle">Fifteen Puzzle Game</a>.
For this task you will be using the following puzzle:

15 14 1 6

9 11  4 12
0 10  7  3

13 8 5 2


Solution:

1  2  3  4
5  6  7  8
9 10 11 12

13 14 15 0

The output must show the moves' directions, like so: left, left, left, down, right... and so on.
There are 2 solutions with 52 moves:
rrrulddluuuldrurdddrullulurrrddldluurddlulurruldrdrd
rrruldluuldrurdddluulurrrdlddruldluurddlulurruldrrdd
finding either one, or both is an acceptable result.
see: <a rel="nofollow" class="external text" href="http://www.rosettacode.org/wiki/15_puzzle_solver/Optimal_solution">Pretty Print of Optimal Solution</a>

Extra credit.

Solve the following problem:

 0 12  9 13
15 11 10 14
 3  7  2  5
 4  8  6  1


Related Task
  • <a href="/wiki/15_Puzzle_Game" title="15 Puzzle Game">15 puzzle game</a>
  • <a href="/wiki/A*_search_algorithm" title="A* search algorithm">A* search algorithm</a>




2048

The rules are that on each turn the player must choose a direction (up, down, left or right) and all tiles move as far as possible in that direction, some more than others. Two adjacent tiles (in that direction only) with matching numbers combine into one bearing the sum of those numbers. A move is valid when at least one tile can be moved, if only by combination. A new tile with the value of 2 is spawned at the end of each turn at a randomly chosen empty square, if there is one. To win the player must create a tile with the number 2048. The player lo ses if no valid moves are possible.

The name comes from the popular open-source implementation of this game mechanic, <a rel="nofollow" class="external text" href="https://gabrielecirulli.github.io/2048/">2048</a>.

Requirements:

and so on