C++ program to multiply two polynomials maintained as linked lists

#include <iostream.h>
class poly
{
private :
struct polynode
{
float coeff ;
int exp ;
polynode *link ;
} *p ;
public :
poly( ) ;
void poly_append ( float c, int e ) ;
void display_poly( ) ;
void poly_multiply ( poly &p1, poly &p2 ) ;
void padd ( float c, int e ) ;
~poly( ) ;
} ;
poly :: poly( )
{
p = NULL ;
}
void poly :: poly_append ( float c, int e )
{
polynode *temp ;
temp = p ;
if ( temp == NULL )
{
temp = new polynode ;
p = temp ;
}
else
{
while ( temp -> link != NULL )
temp = temp -> link ;
temp -> link = new polynode ;
temp = temp -> link ;
}
temp -> coeff = c ;
temp -> exp = e ;
temp -> link = NULL ;
}
void poly :: display_poly( )
{
polynode *temp = p ;
int f = 0 ;
while ( temp != NULL )
{
if ( f != 0 )
{
if ( temp -> coeff > 0 )
cout << " + " ;
else
cout << " " ;
}
if ( temp -> exp != 0 )
cout << temp -> coeff << "x^" << temp -> exp ;
else
cout << temp -> coeff ;
temp = temp -> link ;
f = 1 ;
}
}
void poly :: poly_multiply ( poly &p1, poly &p2 )
{
polynode *temp1, *temp2 ;
float coeff1, exp1 ;
temp1 = p1.p ;
temp2 = p2.p ;
if ( temp1 == NULL && temp2 == NULL )
return ;
if ( temp1 == NULL )
p = p2.p ;
else
{
if ( temp2 == NULL )
p = temp1 ;
else		{
while ( temp1 != NULL )
{
while ( temp2 != NULL )
{
coeff1 = temp1 -> coeff * temp2 -> coeff ;
exp1 = temp1 -> exp + temp2 -> exp ;
temp2 = temp2 -> link ;
padd ( coeff1, exp1 ) ;
}
temp2 = p2.p ;
temp1 = temp1 -> link ;
}
}
}
}
void poly :: padd ( float c, int e )
{
polynode *r, *temp ;
temp = p ;
if ( temp == NULL || c > temp -> exp )
{
r = new polynode ;
r -> coeff = c ;
r -> exp = e ;
if ( p == NULL )
{
r -> link = NULL ;
p = r ;
}
else
{
r -> link = temp ;
p = r ;
}
}
else
{
while ( temp != NULL )
{
if ( temp -> exp == e )
{
temp -> coeff += c ;
return ;
}
if ( temp -> exp > c && ( temp -> link -> exp < c ||
temp -> link == NULL ) )
{
r = new polynode ;
r -> coeff = c;
r -> exp = e ;
r -> link = NULL ;
temp -> link = r ;
return ;
}
temp = temp -> link ;
}
r -> link = NULL ;
temp -> link = r ;
}
}
poly :: ~poly( )
{
polynode *q ;
while ( p != NULL )
{
q = p -> link ;
delete p ;
p = q ;
}
}
void main( )
{
poly p1 ;
p1.poly_append ( 3, 5 ) ;
p1.poly_append ( 2, 4 ) ;
p1.poly_append ( 1, 2 ) ;
 
cout << "\nFirst polynomial: " << endl ;
p1.display_poly( ) ;
poly p2 ;
p2.poly_append ( 1, 6 ) ;
p2.poly_append ( 2, 5 ) ;
p2.poly_append ( 3, 4 ) ;
cout << "\nSecond polynomial: " << endl ;
p2.display_poly( ) ;
poly p3 ;
p3.poly_multiply ( p1, p2 ) ;
cout << "\nResultant polynomial: " << endl ;
p3.display_poly( ) ;
}