Detailed explanation of binary search algorithm examples in PHP

This article mainly introduces the binary search algorithm in PHP. It summarizes and analyzes the principles and specific implementation techniques of the binary search algorithm in the form of examples. Friends in need can refer to the following

Biometric search in advanced points It may be used in development. Of course, when looking for a job in a large company, there will be interview questions like this. Let's take a look at an article about how to implement binary search in PHP. The specific details are as follows.

Dichotomy (dichotomie) is a method of dividing into two. Let [a, b] be the closed interval of R. The successive dichotomy method is to create the following interval sequence ([an, bn]): a0= a, b0=b, and for any natural number n, [an 1, bn 1] is either equal to [an, cn], or equal to [cn, bn], where cn represents the midpoint of [an, bn].

Example 1:

header('Content-Type: text/html; charset=utf-8;');
$arr = array(2,33,22,1,323,321,28,36,90,123);
sort($arr);
//二分法查找
echo $index = binarySearch($arr,321);
function binarySearch($arr,$key){
 $len = count($arr);
 $mid = -1;
 $start = 0;
 $end  = $len-1;
 while($start<=$end){
 $mid = (int)(($start+$end)/2);
 echo $mid."\n";
 if($arr[$mid] == $key){
  return $mid;
 }else if($arr[$mid] < $key){
  $start = $mid+1;
 }else if($arr[$mid] > $key){
  $end = $mid-1;
 }
 }
}

Example 2:

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