How to find the median of a large array in php

Method: 1. Use sort() to sort the array, and use count() to find the length of the array; 2. Use "length%2==0" to determine whether the length is an even number or an odd number, and if it is an even number, the median It is "(array name [(length)/2] array name [((length)/2) 1])/2", otherwise it is "array [(length/2)-0.5".

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

php seeks a large array Median method

Implementation idea:

• Use sort() to sort the array, Then use count() to find the length of the array

• Determine whether the length of the array is even or odd

  If the length of the array is even, then the median will bearr[ Array length/2] arr[(array length/2) 1]/ 2.

  If the array length is odd, the median will be the middle element arr[(array length / 2) - 0.5].

Implementation code:

<?php
header("Content-type:text/html;charset=utf-8");
function f($arr){
	sort($arr);
	$len=count($arr);
	if($len%2==0){
		 // 如果长度是偶数
		 echo "中位数为： ".(($arr[$len/2]+$arr[($len/2)- 1])/2)."<br>";
	}else{
		// 如果长度是奇数
		echo "中位数为： ".($arr[($len/2)-0.5])."<br>";
	}
}
$arr1=[1, 4, 7, 9];
f($arr1);
$arr2=[1, 2, 4, 7, 9];
f($arr2);
?>

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