protected static function c(int $n) : float
    {
        if ($n <= 1) {
            return 1.;
        }
        
        return 2. * (log($n - 1) + M_EULER) - 2. * ($n - 1) / $n;
    }
protected static function c(int $n) : float
    {
        if ($n <= 1) {
            return 1.;
        }
        
        return 2. * (log($n - 1) + M_EULER) - 2. * ($n - 1) / $n;
    }
protected static function c ( int $ n ) : float { if ( $ n <= 1 ) { return 1. ; } return 2. * ( log ( $ n - 1 ) + M_EULER ) - 2. * ( $ n - 1 ) / $ n ; }
Calculate the average path length of an unsuccessful search for n nodes.

@param int $n
@return float
Calculate the average path length of an unsuccessful search for n nodes .