二分查找
function bin_search ($arr, $num)
{
if (!in_array($num, $arr)) {
return 'error num input';
}
$len = count($arr);
$start = 0;
$end = $len-1;
while ($start <= $end) {
$mid = ceil( ($end+$start)/2 );
if ($arr[$mid] < $num) {
$start = $mid + 1;
}elseif ($arr[$mid] > $num) {
$end = $mid - 1;
}else {
return $mid;
}
}
return false;
}
$arr = [1,2,3,4,5,6];
echo bin_search($arr, 1);
由于二分查找需要的是有序数组，所以顺便贴一个 快速排序法
快速排序
function quickSort( array $arr) {
if (!isset($arr[1])) {
return $arr;
}
$left = $right = $midium = [];
$rand = $arr[0];
foreach ($arr as $v) {
if ($rand < $v) {
$right[] = $v;
}
if ($rand > $v) {
$left[] = $v;
}
//此步为了处理重复值
if ($rand == $v) {
$midium[] = $v;
}
}
$left = quickSort($left);
$right = quickSort($right);
return array_merge($left, $midium, $right);
}
$arr2 = [2,0,54,2342,56,22,5];
var_dump(quickSort($arr2));