The PHP Challenge

[Barand]

No trick. There is a solution, but it's bigger than MAXINT

[.josh]

so...does finding the answer involve running it on a 64 bit processor then?

[tauchai83]

hehehe..all the good PHP programmer is challenging each other....let's write a shopping cart coding.

[Barand]

Didn't even have 8 bit processors when it was originally set :D

[Orio]

So what's the next [i]possible[/i] challenge Barand? ;)

Orio.

[Barand]

The original solution was found using pencil, paper and algebra, so there's no impossibility, just a degree of difficulty.

[Barand]

HINT 1: for the "brute force" computational approach the bcmath library may help

HINT 2: to cut down on run time, you are looking for a 16 digit number

[.josh]

damn...someone figured that out using pencil and paper and it's a 16 digit number? That's epic...

[Barand]

I can remember the question and I can remember the answer (even after 40 years) but the route twixt the two is a little foggy.

I know you start off with

3 * (a[sub]n[/sub]10[sup]n[/sup] + a[sub]n-1[/sub]10[sup]n-1[/sup] + ... + a[sub]1[/sub]10 + a[sub]0[/sub]) = 2 * (a[sub]n-1[/sub]10[sup]n[/sup] + a[sub]n-2[/sub]10[sup]n-1[/sup] + ... + a[sub]0[/sub]10 + a[sub]n[/sub])

if that helps :D

[.josh]

okay well all of that wierd looking thing looks well...wierd. and not just cuz it's wavy. The wavy actually helped. 

so I opted for the bcmath/bruteforce method.  It's been running for about 15 min. now...

[Philip]

I [b]think[/b] understand what you're saying Barand, however, did you write the Sigma in the correctly on the right side?  Should it be
2 * (a[sub]n-1[/sub]10[sup]n[/sup] + a[sub]n-2[/sub]10[sup]n-1[/sup] + ... + a[sub]0[/sub]10 + a[sub]-1[/sub])
?


I dunno, I'm only in high school Calculus, but I'm afraid I'm trying to over-complicate it. However, I must admit, it does look like some tangent function, at least from what I could tell from looking at all the numbers. Asymptotes are at x=0 and x=5. Am I on the right path?

[Barand]

The last term should be a[sub]n[/sub] as that is the digit that was moved from the first position to the last.

If I remember correctly, the solution went like this, but I remember you finally have to divide 3*10[sup]n[/sup] by 17, so I'm not sure how to get rid of that annoying  "2*a[sub]n[/sub]"

3 * (a[sub]n[/sub]10[sup]n[/sup] + a[sub]n-1[/sub]10[sup]n-1[/sup] + ... + a[sub]1[/sub]10 + a[sub]0[/sub]) = 2 * (a[sub]n-1[/sub]10[sup]n[/sup] + a[sub]n-2[/sub]10[sup]n-2[/sup] + ... + a[sub]0[/sub]10 + a[sub]n[/sub])
   
Let X = a[sub]n-1[/sub]10[sup]n-1[/sup] + ... + a[sub]1[/sub]10 + a[sub]0[/sub],

then

3 * a[sub]n[/sub]10[sup]n[/sup] + 3*X = 2*10*X + 2*a[sub]n[/sub]

3 * a[sub]n[/sub]10[sup]n[/sup] - 2*a[sub]n[/sub] = 17*X

[Philip]

Hmm, okay. Makes sense... kinda.

I guess I'll have to see if my calc teacher can get it. He can do crazy things in his head.

And btw, - Someone posts a Simple - Intermediate PHP challenge. IS one of the rules... but I don't think you broke it, the PHP isn't hard... its the math getting to the PHP that is :P

Nice workaround for the rules :P

[Barand]

It can be done with brute force, patience and a liquid-cooled processor.

BTW, CV - how's it going. Is your cpu smoking yet? (the 3 * 10[sup]n[/sup]/17 is a hell of a hint)

[Barand]

In case it hasn't finished by breakfast time

Answer : 1,176,470,588,235,294

[.josh]

LoL I gave up.  After an hour of my processor running at 100% I stopped it.  I don't even know what number it got up to. Maybe I should have used some js or something to write the current number to the screen or something.

[chiprivers]

What is the latest challenge?

[redbullmarky]

[code]
<?php
echo '1,176,470,588,235,294';
?>
[/code]
does that count now? ;D

[chiprivers]

If nobody else is setting a challenge, how about creating a function that compare two poker hands and returns the winning hand?

The function could either accept two arguments where a hand is submitted in the form "3h7d9cJhAs" or each card could be submitted as an individual argument?

[steviewdr]

It would be easier if it was Texas Holdem, as there would only be 2 cards that the player have. Quite do-able tho, if I had the time.

-steve

[chiprivers]

[quote author=steviewdr link=topic=119299.msg507829#msg507829 date=1169133842]
It would be easier if it was Texas Holdem, as there would only be 2 cards that the player have. Quite do-able tho, if I had the time.

-steve
[/quote]

Well how about a function for Texas Holdem then where you enter 7 arguments, 5 community cards and the 2 players cards and the function returns a point value for the best hand that can be created, this point value can the be compared against the points returned from another players hand to see who would win?

[The Little Guy]

I don't think anyone knows, so if know one gets it, here is another challenge to maybe pick it up again:

Create a strtoupper function without using any function that will uppercase a letter. This should be able to uppercase anything, and ever letter.

[Orio]

I am happy someone finally gave a challenge that is short and fair...

[code]<?php

function upper($str)
{
$letters = str_split($str);
$new = array();
foreach ($letters as $char)
{
if($char >= ord("a")  &&  $char <= ord("z");
$char = chr(ord($char) - 32);
$new[] = $char;
}

return implode("", $new);
}

?>[/code]

Next challenge- Make a function that will do the same job as [url=http://www.php.net/manual/en/function.trim.php]trim()[/url] does (without using trim, rtrim, ltrim or chop) - Remove all kinds of spaces from the begining and end of a string, as written in the manual.

Orio.

[makeshift_theory]

[code]
<?php
function my_trim($str,$charlist)
{
$str = ereg_replace(" ","",$str);
                if(!empty($charlist) || $charlist != '')
              {
                  if(is_array($charlist))
                  {
                    foreach($charlist as $char)
                      $str = ereg_replace($char,"",$str);
                  }
                  else
                    $str = ereg_replace($char,"",$str);
}
                  return $str;
}
$trim = "LOT OF SPACES HERE            WOOT    FOR  SPACES    ";
echo my_trim($trim,'');
?>
[/code]

Pretty simple but it removes all spaces from a phrase.  It can be tested here [url=http://www.startrekrpg.com/ajax/trim.php]www.startrekrpg.com/ajax/trim.php[/url]

PS> I read on trim that you can use choose what characters you want to remove specifically.  So with this function you can pass an array of characters that you wish to remove or just one.

[Daniel0]

[code]trim("LOT OF SPACES HERE            WOOT    FOR  SPACES    ");[/code] returns: [code]LOT OF SPACES HERE            WOOT    FOR  SPACES[/code]

So I am afraid your function isn't valid.