PHP implements quick sorting php array sorting php array reordering php bubble sort calculation

Quick sort: In the unordered array $data, select any value as the comparison value, define i as the head retrieval index, j as the tail retrieval index, algorithm steps:

(1) Initialize the comparison value $value=$ data[0], $i=1, $j=count($data)-1

(2) First search from the end, judge whether $data[$j] is less than $value, if not, then $j- -, continue to search until you find coordinates

that are smaller than $value (3) At this time, start the head search to determine whether $data[$i] is greater than $value, if not, then $i++, continue to search until you find a coordinate that is smaller than $value. Coordinates with larger $value

(4) At this time, the values ​​​​of $data[$j] and $data[$i] are exchanged with each other, that is, the values ​​larger than $value are placed on the right, and the values ​​smaller than $value are placed on the left.

(5) Repeat 3 and 4 until $i==$j

(6) At this time, the one larger than $value has been placed on the right, and the smaller than $value has been placed on the left, and the coordinate position in the middle has been determined is $i, the middle value is $value, exchange the value of $data[$i] with the value of $data[0], because the middle value is $value, you need to move $value to the middle coordinate of the array

(7 ) The array is divided into two unordered arrays on the left and right, and then recursively execute 1-6 respectively until the array length is 1

Tips: The Chinese definition of quick sort will be clearer in Baidu

Code:

<?php
header("Content-type: text/html; charset=utf-8"); 

function quickSort($data, $startIndex, $endIndex){
	if($startIndex < $endIndex){
		$value = $data[$startIndex];  // 对比值
		$startT = $startIndex + 1;
		$endT = $endIndex;
		
		while ($startT != $endT) {
			// 找到比对比值小的坐标
			while ($data[$endT] > $value && $endT > $startT){
				$endT--;
			}

			// 找到比对比值大的左边
			while ($data[$startT] < $value && $startT < $endT){
				$startT++;
			}

			if($endT > $startT){
				$temp =$data[$startT];
				$data[$startT] = $data[$endT];
				$data[$endT] = $temp;
			}
		}
		
		// 防止数组已经排序好的情况
		if($data[$startT] < $value){
			$data[$startIndex] = $data[$startT];
			$data[$startT] = $value;
		}
		
		$data = quickSort($data, $startIndex, $startT - 1);
		$data = quickSort($data, $startT + 1, $endIndex);
		return $data;
	}else{
		return $data;
	}
}

$data = array(10, 5, 30, 22, 1, 42, 14, 34, 8, 13, 28, 36, 7);
$data = quickSort($data, 0, count($data) - 1);
var_dump($data);

The above introduces the implementation of quick sorting in PHP, including quick sorting and PHP content. I hope it will be helpful to friends who are interested in PHP tutorials.