Implementation of php quick sort

Quick sort is a common sorting algorithm and runs faster than other sorting algorithms in most cases, especially for sorting scenarios of large-scale data. Implementing quick sort in PHP is also very simple and only requires a few lines of code. This article will introduce the implementation of quick sort in php.

What is quick sort

Quick sort is a sorting algorithm based on divide and conquer, which divides the sequence to be sorted into several subsequences, and each subsequence is sorted according to a benchmark value. The base value can be any number, usually the first or last element is taken, and then the data is divided into two groups, one side is greater than the base value, and the other side is less than the base value. By calling this process recursively and finally merging the subsequences, an ordered sequence can be obtained.

PHP quick sorting implementation

The code is as follows:

function quickSort($arr)
{
    $length = count($arr);
    if ($length <= 1) {
        return $arr;
    }
    $left = $right = array();
    $pivot = $arr[0];
    for ($i = 1; $i < $length; $i++) {
        if ($arr[$i] < $pivot) {
            $left[] = $arr[$i];
        } else {
            $right[] = $arr[$i];
        }
    }
    return array_merge(quickSort($left), array($pivot), quickSort($right));
}

In the above code, $arr is the array to be sorted, and the $left and $right arrays are used respectively. Store numbers smaller and larger than the base value. $pivot is the base value. The numbers in the array are divided into two categories according to size through a loop. Finally, the numbers in the left and right parts are combined.

The time complexity of quick sort is O(nlogn), and it is also very efficient in actual use.

Summary

Quick sort is a common sorting algorithm based on divide and conquer. By selecting a benchmark number, the array to be sorted is divided into two subsequences, and the subsequences are sorted recursively. Finally, the two subsequences are merged into an ordered sequence. It is also very simple to implement quick sort in PHP. The code given above is for reference. The time complexity of the quick sort algorithm is O(nlogn) and it performs well in actual use.

The above is the detailed content of Implementation of php quick sort. For more information, please follow other related articles on the PHP Chinese website!