array - maximum times in a row?

bookbuyer2000

How do I find the maximum times in a row an element occurs in an array?

Example:
$array = array('a' , 'b' , 'b' , 'a' , 'a' , 'a' , 'a' , 'b' , 'b' , 'b' , 'c' , 'b');

// ...the desired answer:
// element 'a' appears a maximum of 4 times in a row
// element 'b' appears a maximum of 3 times in a row
// element 'c' appears a maximum of 1 times in a row

Thank you!!🙂

HalfaBee

www.php.net/array_count_values

bookbuyer2000

Thank you -- I already studied that page you suggested -- but I am not wanting to know the total count of each element.

Instead, I am wanting to know the maximum number of times-in-a-row an element occurs.

For example (using the array I posted above), the element 'b' appears a total of 5 times, but the maximum number of times-in-a-row for element 'b' is 3.

How do I find out the maximum number of times in a row an element occurs?

HalfaBee

You will have to parse it yourself, basically foreach thru the array keeping track of the last element to see when it changes and inc an array using the element as the key.

Sounds like someones homework 🙂

bookbuyer2000

Thank you for trying to help -- but the "you'll have to parse it yourself" is what I'm having trouble with 🙂

I cannot seem to figure out how to do a foreach loop that applies. :queasy:

HalfaBee

Probably something along these lines.
Completely untested.

<?php

$array = array('a' , 'b' , 'b' , 'a' , 'a' , 'a' , 'a' , 'b' , 'b' , 'b' , 'c' , 'b');
$array = array('a' , 'b' , 'b' , 'a' , 'b');

$array = array('b' , 'b' , 'a' , 'a' , 'a');

$last = '';
$key = '';
foreach( $array as $value ) {
    if( $value != $last ) { // start new section
        if( $key AND $parts[$key] < $count ) { // if run is longer, store it
            $parts[$key]=$count;
            $parts[$value]= 1;
        }
        $count = 1;
        $key = $value;
    } else {
        $count++;
    }
    $last = $value;
}
if( $parts[$key] < $count ) {
    $parts[$key] = $count;
}

var_dump( $parts );
?>

HalfaBee

changed the code. 🙂

bookbuyer2000

I'll give it a try.

HalfaBee

It should work now.
I even tested it. 🙂

bookbuyer2000

AMAZING! How did you figure that out? And how did you do that so quickly?
Thank you!! 🙂

HalfaBee

It is called years of experience.

bookbuyer2000

For some reason, that code doesn't work with this array:
$array = array('a','a','a','a','b');

The var_dump gives this:

array(1) {
["a"]=>
int(4)
}

...but doesn't list the "b" element... ?? 😕

HalfaBee

Because there is no ending char.

    if( $value != $last ) { // start new section
        if( $key AND $parts[$key] < $count ) { // if run is longer, store it
            $parts[$key]=$count;
        }
        $count = 1;
        $key = $value;
        $parts[$key]=1; // add this line

bookbuyer2000

Uh-oh.... I added that line of code, and now this array doesn't work:

$array = ('a' , 'b' , 'b' , 'a' , 'b');

Here is the var_dump:

array(2) {
["a"]=> int(1)
["b"]=> int(1)
}

😕

... and this array doesn't work either:

$array = ('b' , 'b' , 'a' , 'a' , 'a');

here is the var_dump:

array(2) {
["b"]=> int(2)
["a"]=> int(1)
}

HalfaBee

Now at home, with a minor change it should now work.
I edited the original code.

Weedpacket

How about this version for finding the longest consecutive run of each value:

function count_consecutive_values($array)
{
	if(!count($array)) return $array; // There's nothing here!

// Kick things off...
$previous = array_shift($array);
$counts[$previous][0] = 1;
foreach($array as $current)
{
	// Today I am too lazy to check that the index is
	// there before incrementing its value.
	@$counts[$current][$indices[$current]]++;
	if($current!=$previous)
	{
		@$indices[$previous]++;
		$previous = $current;
	}
}
//	print_r($counts);
	return array_map('max',$counts);
}

djjjozsi

It has a little mistake( Undefined variable ), but a little bit shorter:

<?
$array = array('a' , 'b' , 'b' , 'a' , 'a' , 'a' , 'a' , 'b' , 'b' , 'b' , 'c' , 'b');
foreach($array AS $vars)
{
$var[$vars]++;
}
print "<pre>";
print_r($var);
print "</pre>";
?>

Array
(
[a] => 5
=> 6
[c] => 1
)

Weedpacket

djjjozsi wrote:
It has a little mistake( Undefined variable ), but a little bit shorter:

Unfortunately, apart from the little mistake, it's equivalent to array_count_values(), which has already been determined to be inadequate.

I thought I'd do a second version with an auxiliary function.

function partition_on_distinct($array)
{
	if(!count($array)) return array();
	$a = array_shift($array);
	if(!count($array)) return array(array($a,1));
	$parts = partition_on_distinct($array);
	if($parts[0][0]==$a)
	{
		$parts[0][1]++;
	}
	else
	{
		array_unshift($parts, array($a,1));
	}
	return $parts;
}

function count_consecutive_values($array)
{
	$parts = partition_on_distinct($array);
	$counts = array();
	foreach($parts as $part)
	{
		$counts[$part[0]][] = $part[1];
	}
	return array_map('max',$counts);
}

print_r(count_consecutive_values($array));