How to find duplicate elements in array in effective way. I mean to say with very less iterations

<?php

    Using Characters here, as give more flexibility.

    Character[] arrayC= (new Character[] { 'a', 'a', 'a', 'b', 'b' ,'v'});

    List<Character> allChars= new ArrayList<>(Arrays.asList(arrayC));

    List<Character> duplicates = allChars.stream().distinct().filter(

                                entry -> Collections.frequency(allChars, entry) > 1).

                                collect(Collectors.toList());

    // duplicates  --> 'a','b'

    First the array is converted into an ArrayList. Then, if finds some entry that is repeated more than once, it collects it into duplicates.

    If you want to get which are not duplicates, just:

    allChars.removeAll(duplicates);

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How to find duplicate elements in array in effective way. I mean to say with very less iterations

<?php

    Using Characters here, as give more flexibility.

    Character[] arrayC= (new Character[] { 'a', 'a', 'a', 'b', 'b' ,'v'});

    List<Character> allChars= new ArrayList<>(Arrays.asList(arrayC));

    List<Character> duplicates = allChars.stream().distinct().filter(

                                entry -> Collections.frequency(allChars, entry) > 1).

                                collect(Collectors.toList());

    // duplicates  --> 'a','b'

    First the array is converted into an ArrayList. Then, if finds some entry that is repeated more than once, it collects it into duplicates.

    If you want to get which are not duplicates, just:

    allChars.removeAll(duplicates);

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How can I create every combination possible for the contents of two arrays?

<?php

    A loop of this form

    combos = [] //or combos = new Array(2);

    for(var i = 0; i < array1.length; i++)

    {

        for(var j = 0; j < array2.length; j++)

        {

            //you would access the element of the array as array1[i] and array2[j]

            //create and array with as many elements as the number of arrays you are to combine

            //add them in

            //you could have as many dimensions as you need

            combos.push(array1[i] + array2[j])

        }

    }

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How can I create every combination possible for the contents of two arrays?

<?php

    A loop of this form

    combos = [] //or combos = new Array(2);

    for(var i = 0; i < array1.length; i++)

    {

        for(var j = 0; j < array2.length; j++)

        {

            //you would access the element of the array as array1[i] and array2[j]

            //create and array with as many elements as the number of arrays you are to combine

            //add them in

            //you could have as many dimensions as you need

            combos.push(array1[i] + array2[j])

        }

    }

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How to Sort Multi-dimensional Array by Value?

Active 1 month ago

Viewed 860k times

1184

350

 

350

How can I sort this array by the value of the "order" key? Even though the values are currently sequential, they will not always be.

Array
(
    [0] => Array
        (
            [hashtag] => a7e87329b5eab8578f4f1098a152d6f4
            [title] => Flower
            [order] => 3
        )

    [1] => Array
        (
            [hashtag] => b24ce0cd392a5b0b8dedc66c25213594
            [title] => Free
            [order] => 2
        )

    [2] => Array
        (
            [hashtag] => e7d31fc0602fb2ede144d18cdffd816b
            [title] => Ready
            [order] => 1
        )
)

Answer

11 Answers

1814

Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual

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How to Sort Multi-dimensional Array by Value?

Active 1 month ago

Viewed 860k times

1184

350

 

350

How can I sort this array by the value of the "order" key? Even though the values are currently sequential, they will not always be.

Array
(
    [0] => Array
        (
            [hashtag] => a7e87329b5eab8578f4f1098a152d6f4
            [title] => Flower
            [order] => 3
        )

    [1] => Array
        (
            [hashtag] => b24ce0cd392a5b0b8dedc66c25213594
            [title] => Free
            [order] => 2
        )

    [2] => Array
        (
            [hashtag] => e7d31fc0602fb2ede144d18cdffd816b
            [title] => Ready
            [order] => 1
        )
)

Answer

11 Answers

1814

Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual

Read More