PHP Data structure and algorithm (PHP description) lookup and binary search _php tips

Copy Code code as follows:

<?php
/**
* Find
*
**/
Sequential Lookup
function Normal_search ($arrData, $val) {
$len = count ($arrData);
if ($len = = 0) return-1;
for ($i = 0; $i < $len; $i + +) {
echo "Find No.", $i + 1, "value =", $arrData [$i], "is =", $val, "? <br/> ";
Got it
if ($arrData [$i] = = $val) return $i;
}
return-1;
}

Test Order Lookup
$arrData = Array (4,51,6,73,2,5,9,33,50,3,4,6,1,4,67);
Echo Normal_search ($arrData, 6), "<br/>";
echo Normal_search ($arrData), "<br/>";

Binary lookup (search for ordered columns)
function Binary_search ($arrData, $val) {
$len = count ($arrData);
if ($len = = 0) return-1;

$start = 0;
$end = $len-1;

while ($start <= $end) {
$middle = Intval (($start + $end)/2);
echo "start =", $start, "end =", $end, "middle =", $middle, "<br/>";
if ($arrData [$middle] = = $val) {
return $middle;
} elseif ($arrData [$middle] > $val) {
$end = $middle-1;
} elseif ($arrData [$middle] < $val) {
$start = $middle + 1;
}
}
return-1;
}

Test the two-way search
$arrData = Array (1,2,3,4,5,7,8,9,11,23,56,100,104,578,1000);
Echo Binary_search ($arrData, 578), "<br/>";
echo Binary_search ($arrData), "<br/>";