PHP面试中常见的面试试题与算法例子

function reverse($str){
    $r = array();
    for($i=0; $i         $r[] = mb_substr($str, $i, 1, 'UTF-8');
    }
    return implode(array_reverse($r));
}
echo reverse('www.111cn.net天涯PHP博客');
//结果：'客博PHP涯天moc.ahphp.wwww'

function getext($url){
    $data = parse_url($url);
    $path = $data['path'];
    $info = pathinfo($path);
    return $info['extension'];
}
echo getext('http://www.111cn.net/ ');
//结果：'html'

function getrpath($path, $conpath){
    $pathArr = explode('/', $path);
    $conpathArr = explode('/', $conpath);
    $dismatchlen = 0;
    for($i=0; $i         if($conpathArr[$i] != $pathArr[$i]){
            $dismatchlen = count($pathArr) - $i;
            $arrleft = array_slice($pathArr, $i);
            break;
        }
    }
    return str_repeat('../', $dismatchlen).implode('/', $arrleft);
}
$a = '/a/b/c/d/e.php';
$b = '/a/b/12/34/5.php';
echo getrpath($a, $b);
//结果：'../../../c/d/e.php'

function bubble_sort($arr) {
    $n=count($arr);
    for($i=0;$i         for($j=$i+1;$j             if($arr[$j]                 $temp=$arr[$i];
                $arr[$i]=$arr[$j];
                $arr[$j]=$temp;
            }
        }
    }
    return $arr;
}

function Merge(&$arr, $left, $mid, $right) {
  $i = $left;
  $j = $mid + 1;
  $k = 0;
  $temp = array();
  while ($i   {
    if ($arr[$i]       $temp[$k++] = $arr[$i++];
    else
      $temp[$k++] = $arr[$j++];
  }
  while ($i     $temp[$k++] = $arr[$i++];
  while ($j     $temp[$k++] = $arr[$j++];
  for ($i = $left, $j = 0; $i     $arr[$i] = $temp[$j];
}
 
function MergeSort(&$arr, $left, $right)
{
  if ($left   {
    $mid = floor(($left + $right) / 2);
    MergeSort($arr, $left, $mid);
    MergeSort($arr, $mid + 1, $right);
    Merge($arr, $left, $mid, $right);
  }
}

function bin_search($arr,$low,$high,$value) {
    if($low>$high)
        return false;
    else {
        $mid=floor(($low+$high)/2);
        if($value==$arr[$mid])
            return $mid;
        elseif($value             return bin_search($arr,$low,$mid-1,$value);
        else
            return bin_search($arr,$mid+1,$high,$value);
    }
}

function quick_sort($arr) {
    $n=count($arr);
    if($n         return $arr;
    $key=$arr[0];
    $left_arr=array();
    $right_arr=array();
    for($i=1;$i         if($arr[$i]             $left_arr[]=$arr[$i];
        else
            $right_arr[]=$arr[$i];
    }
    $left_arr=quick_sort($left_arr);
    $right_arr=quick_sort($right_arr);
    return array_merge($left_arr,array($key),$right_arr);
}

function select_sort($arr) {
    $n=count($arr);
    for($i=0;$i         $k=$i;
        for($j=$i+1;$j            if($arr[$j]                $k=$j;
        }
        if($k!=$i) {
            $temp=$arr[$i];
            $arr[$i]=$arr[$k];
            $arr[$k]=$temp;
        }
    }
    return $arr;
}

function insertSort($arr) {
    $n=count($arr);
    for($i=1;$i         $tmp=$arr[$i];
        $j=$i-1;
        while($arr[$j]>$tmp) {
            $arr[$j+1]=$arr[$j];
            $arr[$j]=$tmp;
            $j--;
            if($j                 break;
        }
    }
    return $arr;
}