Count consecutive values in array

Question

I am fetching data from a mysql database that looks like this:

ID	Status
1	Green
2	Red
3	Red
4	Green
5	Green
6	Green
7	Green
8	Grey

And I want to find out, what is the highest consecutive count of Red, Green and Grey.

The outcome should be

Green: 4

Red: 2

Grey: 1

I tried How to count the consecutive duplicate values in an array? and Count Number of Consecutive Occurrence of values in Table but this is not exactly what I need.

I dont want to count every occurance and sum it up. I want to know the highest consecutive count of all of them.

I have tried the following, but it only works for certain scenarios.

$consecResult = array();
$prev_value = array("value" => null, "amount" => null);
while($row = $result->fetch_assoc())
{
    if ($prev_value['value'] != $row['status']) 
    {
       unset($prev_value);
       $prev_value = array('value' => $row['status'], 'amount' => 0);
       $consecResult[$row['status']] =& $prev_value;
    }

    $prev_value['amount']++;
}

Hope that makes sense!

Thanks!

The way I would go about it is to create a counting array before looping with a key being your status and an associated count. Then loop your array and compare the status of the row to see if it is in your return array. If not then add it to your return array with a count of 1. If it already exists in your return array take the count and increment it. Hope I make sense. — DeimosPhx, Jul 11 '23 at 09:13
There is no loop in this code, how do you iterate through the elements in the array? — A.L, Jul 11 '23 at 09:31
The loop is actually a `while($row = $result->fetch_assoc()) {` - let me update my questions — user8918437, Jul 11 '23 at 09:34
Make sure you provide a [mre] of the issue, as per [ask] :-) — ADyson, Jul 11 '23 at 09:35
`UPDATE AND ANSWER`...answers belong in the Answers section, below. Take the [tour] to understand how stackoverflow works. Right now, to a search engine, your question still appears to be unanswered, and also no one can vote on your solution — ADyson, Jul 11 '23 at 09:45

TalESid · Answer 1 · 2023-07-11T11:30:03.273

Here's the algo for your use case. Should work on any other use case:

<?php
$status[0]['status'] = "Green";
$status[1]['status'] = "Green";
$status[2]['status'] = "Green";
$status[3]['status'] = "Green";
$status[4]['status'] = "Red";
$status[5]['status'] = "Red";
$status[6]['status'] = "Grey";
$status[7]['status'] = "Red";
$status[8]['status'] = "Grey";
$status[9]['status'] = "Green";

$curr_count = 0;
$consecResult = array();
$prev_value = null;

foreach($status as $stat) {

    $value = $stat['status'];
    
    # if value doesn't exist in consecResult, add the value with amount = 1 (if already exist, pass)
    if (! array_key_exists($value, $consecResult)) {
        $consecResult[$value] = array('value' => $value, 'amount' => 1);
    }
    
    # if prev_value is same as the value, increment the count variable else set it back to 1
    $curr_count = ($prev_value == $value) ? $curr_count + 1 : 1;
        
    # if amount of the value in consecResult array is lesser than current consecutive count ($curr_count), set new value. Otherwise, pass
    if ($consecResult[$value]['amount'] < $curr_count) {
        $consecResult[$value]['amount'] = $curr_count;
    }
    
    $prev_value = $value;

}

echo "<pre>";
print_r($consecResult);
?>

RESULT

Array
(
    [Green] => Array
        (
            [value] => Green
            [amount] => 4
        )

    [Red] => Array
        (
            [value] => Red
            [amount] => 2
        )

    [Grey] => Array
        (
            [value] => Grey
            [amount] => 1
        )

)

lukas.j · Answer 2 · 2023-07-11T12:33:07.647

$input = [
  [ 'ID' => 1, 'Status' => 'Green' ],
  [ 'ID' => 2, 'Status' => 'Red' ],
  [ 'ID' => 3, 'Status' => 'Red' ],
  [ 'ID' => 4, 'Status' => 'Green' ],
  [ 'ID' => 5, 'Status' => 'Green' ],
  [ 'ID' => 6, 'Status' => 'Green' ],
  [ 'ID' => 7, 'Status' => 'Green' ],
  [ 'ID' => 8, 'Status' => 'Grey' ]
];

$result =
  array_map(
    'max',
    array_reduce(
      array_column($input, 'Status'),
      function ($carry, $status) {
        if ($carry[1] === $status) {
          $carry[0][$status][array_key_last($carry[0][$status])]++;
        } else {
          $carry[0][$status][] = 1;
          $carry[1] = $status;
        }
        return $carry;
      },
      [ [], '' ]
    )[0]
  );

print_r($result);

Output:

Array
(
    [Green] => 4
    [Red] => 2
    [Grey] => 1
)

Short explanation:

array_reduce starts with this initial result array:

[ 
  [],  // will hold all the counts for each color (not only the highest one)
  ''   // will hold the value of 'status' of the prior item in the array
]

And it starts also with this input array:

array_column($input, 'Status')

The result of it looks like this:

Array
(
    [0] => Array
        (
            [Green] => Array
                (
                    [0] => 1   // first occurence of 'Green'
                    [1] => 4   // second occurence of 'Green'
                               // etc.
                )

            [Red] => Array
                (
                    [0] => 2   // first occurence of 'Red'
                               // etc.
                )

            [Grey] => Array    // first occurence of 'Grey'
                               // etc.
                (
                    [0] => 1
                )

        )

    [1] => Grey   // this item is then dropped by using [0]
)

The last step is to apply max to each color item in the result array within array_map.

score 1 · Accepted Answer · answered Jul 11 '23 at 12:31

I have tested both arrays which you have shared i.e.

$status[0]['status'] = "Green";
$status[1]['status'] = "Red";
$status[2]['status'] = "Red";
$status[3]['status'] = "Green";
$status[4]['status'] = "Green";
$status[5]['status'] = "Green";
$status[6]['status'] = "Green";
$status[7]['status'] = "Grey";

AND

$status[0]['status'] = "Green";
$status[1]['status'] = "Green";
$status[2]['status'] = "Green";
$status[3]['status'] = "Green";
$status[4]['status'] = "Red";
$status[5]['status'] = "Red";
$status[6]['status'] = "Grey";
$status[7]['status'] = "Red";
$status[8]['status'] = "Grey";
$status[9]['status'] = "Green";

And my code works as expected.

Here is my code:

$status = array();
$status[0]['status'] = "Green";
$status[1]['status'] = "Green";
$status[2]['status'] = "Green";
$status[3]['status'] = "Green";
$status[4]['status'] = "Red";
$status[5]['status'] = "Red";
$status[6]['status'] = "Grey";
$status[7]['status'] = "Red";
$status[8]['status'] = "Grey";
$status[9]['status'] = "Green";

$highestCounts = array(
    'Green' => 0,
    'Red' => 0,
    'Grey' => 0
);

$currentCounts = array(
    'Green' => 0,
    'Red' => 0,
    'Grey' => 0
);

$previousStatus = '';

foreach ($status as $item) {
    $currentStatus = $item['status'];

    if ($currentStatus === $previousStatus) {
        $currentCounts[$currentStatus]++;
    } else {
        $currentCounts[$currentStatus] = 1;
    }

    $previousStatus = $currentStatus;

    // Update the highest count if necessary
    if ($currentCounts[$currentStatus] > $highestCounts[$currentStatus]) {
        $highestCounts[$currentStatus] = $currentCounts[$currentStatus];
    }
}

// Print the results
foreach ($highestCounts as $status => $count) {
    echo $status . ': ' . $count . "\n";
}

user8918437 · Answer 4 · 2023-07-11T10:26:18.263

The answer is already in my question. The provided code does work if I loop through a nice array. I hope I did not make the array fit the solution ;-)

Anyway. This is how you can reproduce it!

<?php

$status[0]['status'] = "Green";
$status[1]['status'] = "Red";
$status[2]['status'] = "Red";
$status[3]['status'] = "Green";
$status[4]['status'] = "Green";
$status[5]['status'] = "Green";
$status[6]['status'] = "Green";
$status[7]['status'] = "Grey";

$consecResult = array();
$prev_value = array("value" => null, "amount" => null);
foreach($status as $stat)
{
    if ($prev_value['value'] != $stat['status']) 
    {
        unset($prev_value);
        $prev_value = array('value' => $stat['status'], 'amount' => 0);
        $consecResult[$stat['status']] =& $prev_value;
    }

    $prev_value['amount']++;
}

echo "<pre>";
print_r($consecResult);

?>

RESULT

Array
(
    [Green] => Array
        (
            [value] => Green
            [amount] => 4
        )

    [Red] => Array
        (
            [value] => Red
            [amount] => 2
        )

    [Grey] => Array
        (
            [value] => Grey
            [amount] => 1
        )
)

UPDATE TO RESULT

Turns out Answer #1 is not correct and the array was indeed made to fit the solution.

If you test with

$status[0]['status'] = "Green";
$status[1]['status'] = "Green";
$status[2]['status'] = "Green";
$status[3]['status'] = "Green";
$status[4]['status'] = "Red";
$status[5]['status'] = "Red";
$status[6]['status'] = "Grey";
$status[7]['status'] = "Red";
$status[8]['status'] = "Grey";
$status[9]['status'] = "Green";

the result will be

Array
(
    [Green] => Array
        (
            [value] => Green
            [amount] => 1
        )

    [Red] => Array
        (
            [value] => Red
            [amount] => 1
        )

    [Grey] => Array
        (
            [value] => Grey
            [amount] => 1
        )
)

Question is, what is missing? :-)

Try my posted code and hope it works for you. – Sachin Jul 11 '23 at 12:34 — Sachin, Jul 11 '23 at 12:34

Count consecutive values in array

4 Answers4