Count Sequence

I have a string of characters e.g. "abds236789plmn".

No character is ever repeated twice in the string.

What I am after doing is creating a function which converts a number to a value from the string.

If i call function sequence(1) it will return a.

1 = a
14 = n
16 = bn
28 = nn

I tried using str_length and treating the string as array and adding 1 to the index.

Thanks for reading.
LVL 15
ncooAsked:
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Roger BaklundConnect With a Mentor Commented:
I believe this is what you mean:
function BaseX($n,$str="abds236789plmn") {
  $res = '';
  $base = strlen($str);
  while($n > 0) {
    $res = $str[$n % $base].$res;
    $n = floor($n/$base);
  }
  return $res;
}

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sdstuberCommented:
given n, and a string of length l

looks like you are trying to do this...

  the character at the mod(n,l) position (position 0 is no character) followed by
  floor(n/l) copies of the last letter

with your examples above ...

mod(1,14) = 1 =>"a",     floor(n/l) = 0  => "",        final answer "a"
mod(14,14) = 0 => "",    floor(n/l) = 1   => "n",     final answer "n"
mod(16,14) = 2 => "b",  floor(16/14) = 1 => "n",  final answer "bn"
mod(28,14) = 0 => "",    floor(28,14) = 2  => "nn", final answer "nn"
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Roger BaklundCommented:
Try this function:
function sequence($x,$str="abds236789plmn") {
  $res = '';
  $len = strlen($str);
  while($x > 0) {
    $v = ($x % $len);
    if(!$v)$v=$len;
    $res .= $str[$v-1];
    $x -= $v;
  }
  return $res;
}

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ncooAuthor Commented:
I think I may have wording of the question could have been a little better.

The example string length is: 14

Which means for my new string of length 2 there should be 196 combinations of the string (14^2)

I think I may need to have a zero value for this to work.

Like Hex but with a variable set of charaters. So instead of 0-9 and a-f that example string.
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Roger BaklundCommented:
Hex has as you probably know 16 digits, but you can easily do math with any number of digits, including 14. If this is what you are doing, then yes, you will need a zero. By tradition numbers are "growing" from right to left, you are going left to right, but that is not a problem for the math.

Maybe it is easier to work with a "normal" sequence 0-9abcd, and then at the end map the result to your random string of 14 characters, and reverse it?
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sdstuberCommented:
does the algorithm I posted above not do it?

Sorry I don't know php syntax.  but given the description, hopefully somebody can do the actual coding.  I imagine it would be 1 or 2 lines of code tops.
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ncooAuthor Commented:
If I'm reading it correctly sbstuber I'm certain you end up with the same thing as the PHP code cxr originally posted results below, which is not what I am after.

Yes for convention stick with normall numbering order.

If you want to try writing pseudocode I can try to convert to PHP sdstuber.
0 = , 1 = a, 2 = b, 3 = d, 4 = s, 5 = 2, 6 = 3, 7 = 6, 8 = 7, 9 = 8, 10 = 9, 11 = p, 12 = l, 13 = m, 14 = n, 15 = an, 16 = bn, 17 = dn, 18 = sn, 19 = 2n, 20 = 3n, 21 = 6n, 22 = 7n, 23 = 8n, 24 = 9n, 25 = pn, 26 = ln, 27 = mn, 28 = nn, 29 = ann, 30 = bnn, 31 = dnn, 32 = snn, 33 = 2nn, 34 = 3nn, 35 = 6nn, 36 = 7nn, 37 = 8nn, 38 = 9nn, 39 = pnn, 40 = lnn, 41 = mnn, 42 = nnn, 43 = annn, 44 = bnnn, 45 = dnnn, 46 = snnn, 47 = 2nnn, 48 = 3nnn, 49 = 6nnn,  etc...

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ncooAuthor Commented:
New string so it's easier to read:

0123456789abcdefgh

Which should give the output:

0 = 0, 1 = 1, 2 = 2, 3 = 3, 4 = 4, 5 = 5, 6 = 6, 7 = 7, 8 = 8, 9 = 9, 10 = a, 11 = b, 12 = c, 13 = d, 14 = e, 15 = f, 16 = g, 17 = h, 18 = 10, 19 = 11, 20 = 12, 21 = 13, 22 = 14, 23 = 15, 24 = 16, 25 = 17, 26 = 18, 27 = 19, 28 = 1a, 29 = 1b, 30 = 1c, 31 = 1d, 32 = 1e, 33 = 1f, 34 = 1g, 35 = 1h, 36 = 20, 37 = 21, 38 = 22, 39 = 23 etc...
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Roger BaklundCommented:
Then why is 16=bn in your original question? Wouldn't it be 15=aa and 16=ab?

This last example seems to be just "normal" base-18 numbers? Same as hex, but 18 digits?
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Roger BaklundCommented:
ncoo, could you please explain your question a bit more, I don't think I understand what you want.
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ncooAuthor Commented:
I think it would be the following,
1 = b
14 = ba
16 = bd

Lets work with the easier string though first.

Yes base 18 for the easier string and base 14 for the first string.

What I am after is 'base of string length' for a string.

Still not sure how much sense that makes.

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ddrudikCommented:
Based on your sample in 22796961:
<pre>
<?php
function numconv($num,$str){
  $len=strlen($str);
	if($num<$len){
	  return $str[$num];
	} else {
	  $a=intval($num/$len);
		$b=$num-($len*$a);
		return $a.$str[$b];
	}
}
$string="0123456789abcdefgh";
echo '1 "1":'.numconv(1,$string).'<hr>';
echo '13 "d":'.numconv(13,$string).'<hr>';
echo '19 "11":'.numconv(19,$string).'<hr>';
echo '37 "21":'.numconv(37,$string).'<hr>';
?>

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ncooAuthor Commented:
Thanks that is almost it ddrudik.

Sample output below goes wrong at 180.
173 = 9b
174 = 9c
175 = 9d
176 = 9e
177 = 9f
178 = 9g
179 = 9h
180 = 100 should be a0
181 = 101 '' a1
182 = 102 '' a2
183 = 103 '' a3
184 = 104 '' a4

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ddrudikCommented:
If a in a0 is hex of 10 then:
<pre>
<?php
function numconv($num,$str){
  $len=strlen($str);
	if($num<$len){
	  return $str[$num];
	} else {
	  $a=intval($num/$len);
		$b=$num-($len*$a);
		return dechex($a).$str[$b];
	}
}
$string="0123456789abcdefgh";
echo '1 "1":'.numconv(1,$string).'<hr>';
echo '13 "d":'.numconv(13,$string).'<hr>';
echo '19 "11":'.numconv(19,$string).'<hr>';
echo '179 "9h":'.numconv(179,$string).'<hr>';
echo '180 "a0":'.numconv(180,$string).'<hr>';
?>

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ddrudikCommented:
cxr's last post worked for me as well.
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ncooAuthor Commented:
Thank you
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ncooAuthor Commented:
Thanks cxr.

Just tried your new code ddrudik almost it now gets to 288.
286 = fg = fg
287 = fh = fh
288 = 100 = g0
289 = 101 = g1
290 = 102 = g2
291 = 103 = g3
292 = 104 = g4

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ddrudikCommented:
ncoo, seems it was beyond hex then, thanks.
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