[RESOLVED] how to make array_filter recursive

jrough

The arychairs is a set of chairs in a circle from 1 to 100. I need to remove every
other chair starting from the first chair, for example, chairs 1,3,5,7 ...100.
I need help troubleshooting it. First of all it doesn't work. There must be a syntax error. I'm not sure if I have array_filter right but I want it to filter out the chair plus 1 in the ret_next function plus remove the very first chair.
The other problem is it needs to be recursive. The next pass has to go around the
circle and remove the 1st,3rd,5th... in order even though the chairs in the array that are left are 2,4, 6, 8 . If I figured it out right I have the right function array_filter.

first I have to get this working and then make it recursive unless this is way off, thanks😕

<?PHP

//fill array
$arychairs= range(1,100);
//get next chair
ret_next(){
return($var +1);	
}
//remove first chair , third chair, fifth chair (every other chair)
count_chairs($arr){
while ($i < count($arr){
	$arr= array_shift($arr);	
	 array_filter($arr, "ret_next");
	$i++};
$chairs= $arr;
print_r $chairs;
return $chairs;
}



$pass1=count_chairs($arychairs);
print_r $pass1;
?>

leatherback

An alternative strategy?


function count_chairs($arr)
  {
  // how many elements in array
  $i = count($arr);

  // Creat an index to positions 0, 2, 4, ... $i
  $index = range(0, $i, 2);

  // Return the data at positions 0, 1, 2, ...
  return($arr[$index]);
  }

//fill array
$arychairs= range(1,100); 

$filtered = count_chairs($arychairs);

echo "<pre>";
  print_r($filtered);
echo "</pre>";

jrough

Thanks for the new strategy :-)
I tested this out and couldn't figure out how to get the array returned I want.
The array_diff is returning the removed chairs, not the chairs leftover?
I tried to return the $arr[$index] as you suggested but that doesn't return any value.
I have enclosed the output. Probably what I want is array_diff($arr[$index],??)
thanks again.

<?PHP
function count_chairs($arr)
  	{

  // how many elements in array
  	$i = count($arr);

  // Create an index to positions 0, 2, 4, ... $i
  	$index = range(0, $i, 2);


echo "<pre>" ."INDEX" ." ";
print_r($index);
echo "</pre>";
return	array_diff($arr,$index);
// Return the data at positions 0, 1, 2, ...
//	return $arr[$index];         ***********

  }

//fill array
$arychairs= range(1,100);
$filtered = count_chairs($arychairs);

echo "<pre>";
 echo "filtered". print_r($filtered);
echo "</pre>";

echo "<pre>";
 echo "Removed". print_r($filtered);
echo "</pre>";


?>

INDEX Array
(
[0] => 0
[1] => 2
[2] => 4
[3] => 6
[4] => 8
[5] => 10
[6] => 12
[7] => 14
[8] => 16
[9] => 18
[10] => 20
[11] => 22
[12] => 24
[13] => 26
[14] => 28
[15] => 30
[16] => 32
[17] => 34
[18] => 36
[19] => 38
[20] => 40
[21] => 42
[22] => 44
[23] => 46
[24] => 48
[25] => 50
[26] => 52
[27] => 54
[28] => 56
[29] => 58
[30] => 60
[31] => 62
[32] => 64
[33] => 66
[34] => 68
[35] => 70
[36] => 72
[37] => 74
[38] => 76
[39] => 78
[40] => 80
[41] => 82
[42] => 84
[43] => 86
[44] => 88
[45] => 90
[46] => 92
[47] => 94
[48] => 96
[49] => 98
[50] => 100
)

Array
(
[0] => 1
[2] => 3
[4] => 5
[6] => 7
[8] => 9
[10] => 11
[12] => 13
[14] => 15
[16] => 17
[18] => 19
[20] => 21
[22] => 23
[24] => 25
[26] => 27
[28] => 29
[30] => 31
[32] => 33
[34] => 35
[36] => 37
[38] => 39
[40] => 41
[42] => 43
[44] => 45
[46] => 47
[48] => 49
[50] => 51
[52] => 53
[54] => 55
[56] => 57
[58] => 59
[60] => 61
[62] => 63
[64] => 65
[66] => 67
[68] => 69
[70] => 71
[72] => 73
[74] => 75
[76] => 77
[78] => 79
[80] => 81
[82] => 83
[84] => 85
[86] => 87
[88] => 89
[90] => 91
[92] => 93
[94] => 95
[96] => 97
[98] => 99
)
filtered1

leatherback

My apologies; I was confused with a matrix language I programme in too. There you can index an array with an array. The adjusted code:


<?php

function count_chairs($arr)
  {
  // how many elements in array
  $i = count($arr);

  // Creat an index to positions 0, 2, 4, ... $i
  $index = range(0, $i, 2);

  // Return the data at positions 0, 1, 2, ...
  $out = array();
  foreach($index as $key)
    {
	$out[] = $arr[$key];
	}

  return($out);
  }

//fill array
$arychairs= range(1,100);

$filtered = count_chairs($arychairs);

echo "<pre>";
  print_r($filtered);
echo "</pre>"; 


?>

PS: If this returns the wrong set, use:
$index = range(1, $i, 2);

jrough

Actually I got it to work but the $ChairsLeft are the chairs removed not the chairs leftover. So I need another function besides array_diff? See the output.

<?PHP
function count_chairs($arr)
  	{

  // how many elements in array
  	$i = count($arr);

  // Create an index to positions 0, 2, 4, ... $i
  	$index = range(0, $i, 2);



// Return the data at positions 0, 1, 2, ...
return $index;    

  }

//fill array
$arychairs= range(1,100);
echo "<pre>" ."arychairs". " ";
print_r($arychairs);
echo "</pre>";

$filtered = count_chairs($arychairs);
echo "<pre>" ."FILTERED" ." ";
print_r($filtered);
echo "</pre>";

$chairsLeft = array_diff($arychairs,$filtered);
echo "<pre>" . "Chairs Left Over";
echo  print_r($chairsLeft);
echo "</pre>";
?>

arychairs Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[4] => 5
[5] => 6
[6] => 7
[7] => 8
[8] => 9
[9] => 10
[10] => 11
[11] => 12
[12] => 13
[13] => 14
[14] => 15
[15] => 16
[16] => 17
[17] => 18
[18] => 19
[19] => 20
[20] => 21
[21] => 22
[22] => 23
[23] => 24
[24] => 25
[25] => 26
[26] => 27
[27] => 28
[28] => 29
[29] => 30
[30] => 31
[31] => 32
[32] => 33
[33] => 34
[34] => 35
[35] => 36
[36] => 37
[37] => 38
[38] => 39
[39] => 40
[40] => 41
[41] => 42
[42] => 43
[43] => 44
[44] => 45
[45] => 46
[46] => 47
[47] => 48
[48] => 49
[49] => 50
[50] => 51
[51] => 52
[52] => 53
[53] => 54
[54] => 55
[55] => 56
[56] => 57
[57] => 58
[58] => 59
[59] => 60
[60] => 61
[61] => 62
[62] => 63
[63] => 64
[64] => 65
[65] => 66
[66] => 67
[67] => 68
[68] => 69
[69] => 70
[70] => 71
[71] => 72
[72] => 73
[73] => 74
[74] => 75
[75] => 76
[76] => 77
[77] => 78
[78] => 79
[79] => 80
[80] => 81
[81] => 82
[82] => 83
[83] => 84
[84] => 85
[85] => 86
[86] => 87
[87] => 88
[88] => 89
[89] => 90
[90] => 91
[91] => 92
[92] => 93
[93] => 94
[94] => 95
[95] => 96
[96] => 97
[97] => 98
[98] => 99
[99] => 100
)

FILTERED Array
(
[0] => 0
[1] => 2
[2] => 4
[3] => 6
[4] => 8
[5] => 10
[6] => 12
[7] => 14
[8] => 16
[9] => 18
[10] => 20
[11] => 22
[12] => 24
[13] => 26
[14] => 28
[15] => 30
[16] => 32
[17] => 34
[18] => 36
[19] => 38
[20] => 40
[21] => 42
[22] => 44
[23] => 46
[24] => 48
[25] => 50
[26] => 52
[27] => 54
[28] => 56
[29] => 58
[30] => 60
[31] => 62
[32] => 64
[33] => 66
[34] => 68
[35] => 70
[36] => 72
[37] => 74
[38] => 76
[39] => 78
[40] => 80
[41] => 82
[42] => 84
[43] => 86
[44] => 88
[45] => 90
[46] => 92
[47] => 94
[48] => 96
[49] => 98
[50] => 100
)

Chairs Left OverArray
(
[0] => 1
[2] => 3
[4] => 5
[6] => 7
[8] => 9
[10] => 11
[12] => 13
[14] => 15
[16] => 17
[18] => 19
[20] => 21
[22] => 23
[24] => 25
[26] => 27
[28] => 29
[30] => 31
[32] => 33
[34] => 35
[36] => 37
[38] => 39
[40] => 41
[42] => 43
[44] => 45
[46] => 47
[48] => 49
[50] => 51
[52] => 53
[54] => 55
[56] => 57
[58] => 59
[60] => 61
[62] => 63
[64] => 65
[66] => 67
[68] => 69
[70] => 71
[72] => 73
[74] => 75
[76] => 77
[78] => 79
[80] => 81
[82] => 83
[84] => 85
[86] => 87
[88] => 89
[90] => 91
[92] => 93
[94] => 95
[96] => 97
[98] => 99
)
1

leatherback

Did you see my previous post?

jrough

no, I missed this one, thanks again. I got it to work by taking the array_diff twice and returning the index but it was kind of a kludge. Let me see about this one.

jrough

Thanks very much it works. Now how to make it recursive down to the last remaining chair. My thought is to use ternary operator. If it is the last chair then output $out else call the function count_chairs again. The only problem I see is that the $arychairs array doesn't need to be passed to the function everytime? Where do I put $arychairs?

 <?php

function count_chairs($arr)
  {
  // how many elements in array
  $i = count($arr);

  // Creat an index to positions 0, 2, 4, ... $i
  $index = range(1, $i, 2);

  // Return the data at positions 0, 1, 2, ...
  $out = array();
  foreach($index as $key)
    {
    $out[] = $arr[$key];
    }

  return(count($arr[$key])==1?$out: count_chairs($arr));
  }

//fill array
$arychairs= range(1,100);

$filtered = count_chairs($arychairs);

echo "<pre>";
  print_r($filtered);
echo "</pre>";


?>

leatherback


$arychairs= range(1,100);

while(count($arychairs >1))
  {
  $arychairs = count_chairs($arychairs);

  echo "<pre>";

print_r($arychairs);

  echo "</pre>";
  }

jrough

this is awesome, thanks, I gave it a try, I'll see what I did wrong.

jrough

This doesn't seem to work, doesn't it have to be in a function?
This is what I got but I get 100 not 1 as a result. In your code I don't get any results at all.

<?php

function count_chairs($arr) {
	// how many elements in array
  		$i = count($arr);

  // Creat an index to positions 0, 2, 4, ... $i
  		$index = range(1, $i, 2);

  // Return the data at positions 0, 1, 2, ...
  	$out = array();
  	foreach($index as $key)
    	{
 		$out[] = $arr[$key];
    	}	
	if (count($arr[$key])==1){
		return $out[]=$arr[$key];
	}else{

  return (count_chairs($out));


}

 }

//fill array
$arychairs= range(1,100);
$filtered = count_chairs($arychairs);

echo "<pre>";
  print_r($filtered);
echo "</pre>";


?>

leatherback

Not exactly sure which patter you try to achieve. By removing always every odd chair from your series, the last in the row will everntually be removed. The reason it did not work, is becaus you edited the script, I think.

try this:


<?php

function count_chairs($arr)
  {
  // how many elements in array
  $i = count($arr);

  // Creat an index to positions 0, 2, 4, ... $i
  $index = range(1, $i, 2);

  // Return the data at positions 0, 1, 2, ...
  $out = array();
  foreach($index as $key)
	{
	if(array_key_exists($key, $arr))
	  {
	  $out[] = $arr[$key];
	  }
	}

  return($out);
  }



$arychairs= range(1,100);

while(count( $arychairs ) > 1 )
  {
  $arychairs = count_chairs($arychairs);

  echo "<pre>";
    print_r($arychairs);
  echo "</pre>";
  } 

?>

jrough

thanks I now have to understand it, but it does work it gets to chair 64. I am sure it is a trick question.