PHP to implement a binary lookup program code

Dichotomy (Dichotomie) is the method of splitting in two. Set the closed range [A,b] to R. The successive binary method is to create the following interval sequence ([an,bn]): A0=a,b0=b, and for either natural number n,[an+1,bn+1] or equal to [AN,CN], or equal to [cn,bn], where the 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);

Two-Way Search
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

<?php
The search function $array the array, $k the value to find, $low the minimum key value for the lookup range, $high the maximum key value for the lookup range
function Search ($array, $k, $low =0, $high =0)
{
if (count ($array)!=0 and $high = = 0)//To determine whether the first call
{
$high = count ($array);
}
if ($low <= $high)//If there are remaining array elements
{
$mid = Intval (($low + $high)/2); Take the middle value of $low and $high
if ($array [$mid] = = $k)//if found then return
{
return $mid;
}
ElseIf ($k < $array [$mid])//If not found, continue to find
{
Return Search ($array, $k, $low, $mid-1);
}
Else
{
Return Search ($array, $k, $mid +1, $high);
}
}
return-1;
}
$array = Array (4,5,7,8,9,10); Test search function
Echo Search ($array, 8); Call the search function and output the search results
?>