php实现两分法查找

两分法查找的前提：顺序方式存储，而且必须是排好序

直接上代码：

function search($array, $target, $low = 0, $high = 0){

    $len = count($array);
    $low = max($low, 0);
    $high = $high == 0 ? $len : min($high, $len);

    while($low <= $high){

        $m = $low + ceil((($high - $low) / 2));
        $mv = $array[$m];

        if($mv > $target){
            $high = $m - 1;
        }else if($mv < $target){
            $low = $m + 1;
        }else{
            return $m;
        }
    }

    return -1;
}

$array = array(1, 2, 4, 5, 7, 8, 9, 10);
echo search($array, 9);