PHP dichotomy implementation of array lookup function tutorial

Dichotomy method. Methods that use the while loop and recursive invocations, respectively. This article mainly introduced PHP based on the binary method to realize the array lookup function, combined with the instance form analysis while loop and recursive call algorithm implementation of the two-part search function of the relevant implementation skills, the need for friends can refer to, hope to help everyone.

<?php//the use of the array must be ordered, or ascending, or descending $arr = Array (1, 3, 5, 7, 9, 13);//recursive invocation (compared to better understanding function Bsearch_r ($v, $arr, $low, $high)  {if ($low > $high) {//return-1 to determine the end condition first;  } $i = Intval (($high + $low)/2); if ($arr [$i] > $v) {return Bsearch_r ($v, $arr, $low, $i-1);//recursion} else if ($arr [$i] < $v) {return Bsearch_r (  $v, $arr, $i +1, $high);  } else {return $i; }}echo bsearch_r (1, $arr, 0, Count ($arr)-1);//0echo ' 

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