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2_fen.php
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2_fen.php
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<?php
$arr = [0,1,2,3,4,5,6,7,8,9,10];
$search = 11;
$index = search($arr, $search);
echo ' index=';
echo $index;
function search(array $arr, $target)
{
$len = count($arr);
if ($len == 0) {
return false;
}
$left = 0; $right = $len;
$mid = ($left + $right) >> 1;
while ($arr[$mid]!= $target) {
$mid = getMid($arr, $left, $right, $target);
echo $right;
if($right > $len)
break;
// break;
// echo 'left'.$left;
// echo 'right'.$right;
// echo ($right > count($arr));
// if ($right > count($arr) || $left < 0) {
// break;
// }
}
return $mid;
}
function getMid($arr,&$left,&$right, $target)
{
$mid = ($left + $right) >> 1;
if ($arr[$mid] < $target) {
$left = $mid;
$mid = ($left + $right) >> 1;
} elseif ($arr[$mid] > $target) {
$right = $mid;
$mid = ($left + $right) >> 1;
}
return $mid;
}
function searchByFor(array $arr, $target)
{
$len = count($arr);
if ($len == 0) {
return false;
}
for ($i = 0; $i < $len; $i++) {
if ($arr[$i] == $target) {
return $i;
}
}
}