PHP实现几种经典算法详解

function bubble_sort( $array)  
{  
        $count = count( $array);  
        if ($count <= 0 ) return false;  
        for($i=0 ; $i<$count; $i ++){  
                for($j=$count-1 ; $j>$i; $j--){  
                        if ($array[$j] < $array [$j-1]){  
                                 $tmp = $array[$j];  
                                 $array[$j] = $array[ $j-1];  
                                $array [$j-1] = $tmp;  
                        }  
                }  
        }  
        return $array;  
} 

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

function bin_sch($array,  $low, $high, $k){   
    if ( $low <= $high){   
        $mid =  intval(($low+$high)/2 );   
        if ($array[$mid] ==  $k){   
            return $mid;   
        }elseif ( $k < $array[$mid]){   
            return  bin_sch($array, $low,  $mid-1, $k);   
        }else{   
            return  bin_sch($array, $mid+ 1, $high, $k);   
        }   
    }   
    return -1;   
}  

function  seq_sch($array, $n,  $k){   
    $array[$n] =  $k;   
    for($i=0;  $i<$n; $i++){   
        if( $array[$i]==$k){   
            break;   
        }   
    }   
    if ($i<$n){   
        return  $i;   
    }else{   
        return -1;   
    }   
}  

function delete_array_element($array , $i)  
{  
        $len =  count($array);   
        for ($j= $i; $j<$len; $j ++){  
                $array[$j] = $array [$j+1];  
        }  
        array_pop ($array);  
        return $array ;  
}