How to sort array in php without using function

PHP is a very popular open source server-side scripting language that is widely used to develop web applications. In PHP, sorting is a very important operation, which can help us process data quickly and accurately.

In PHP, we usually use built-in functions or array methods to sort arrays. However, in this article, I want to discuss another way of sorting without using PHP’s built-in functions and array methods.

In PHP, we can use comparison-based sorting algorithm to sort. These algorithms rely on comparing the size relationship between two elements and then placing them in a certain order. This sorting method is very effective, but it requires the use of functions or array methods to implement.

However, we also have an algorithm called non-comparison sorting. These algorithms can sort without comparing the size relationship between two elements, so they are faster and more memory-efficient than comparison-based sorting algorithms.

One of the non-comparison sorting algorithms is counting sort. This sorting algorithm determines the position of each element in the sort based on its value. The value of each element is how many elements before it are smaller than it in the sorting. We can then use a temporary array to store the number of times each value occurs, and then determine the position of each element based on the count array.

Here is a sample code:

function countingSort($arr) {
    $maxVal = max($arr);
    $count = array_fill(0, $maxVal + 1, 0);
    $output = array_fill(0, count($arr), 0);

    foreach ($arr as $val) {
        $count[$val]++;
    }

    for ($i = 1; $i <= $maxVal; $i++) {
        $count[$i] += $count[$i - 1];
    }

    for ($i = count($arr) - 1; $i >= 0; $i--) {
        $output[$count[$arr[$i]] - 1] = $arr[$i];
        $count[$arr[$i]]--;
    }

    return $output;
}

In counting sort, we first find the largest element in the array and then create a counting array. Next, we loop through the entire array and record the number of occurrences of each element in the count array. Then create an output array and fill it with the values ​​in the count array. Finally, the output array is returned as the sorted result.

Using counting sorting is much faster than sorting methods using PHP built-in functions and array methods. The time complexity of this method is O(n k), where n is the number of elements and k is the maximum value of the elements.

In short, although PHP provides many built-in functions and array methods for sorting operations, using a non-comparative sorting algorithm can be more efficient and save memory. Counting sort is one of the very useful algorithms that can help us sort an array quickly.

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