C++ program to add two polynomials maintained using 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_add( poly &l1, poly &l2 ) ;
~poly( ) ;
} ;
poly :: poly( )
{
p = NULL ;
}
void poly :: poly_append ( float c, int e )
{
polynode *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 ;
 
cout << endl ;
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_add ( poly &l1, poly &l2 )
{
polynode *z ;
if ( l1.p == NULL && l2.p == NULL )
return ;
polynode *temp1, *temp2 ;
temp1 = l1.p ;
temp2 = l2.p ;
while ( temp1 != NULL && temp2 != NULL )
{
if ( p == NULL )
{
p = new polynode ;
z = p ;
}
else
{
z -> link = new polynode ;
z = z -> link ;
}
if ( temp1 -> exp < temp2 -> exp )
{
z -> coeff = temp2 -> coeff ;
z -> exp = temp2 -> exp ;
temp2 = temp2 -> link ;
}
else
{
if ( temp1 -> exp > temp2 -> exp )
{
z -> coeff = temp1 -> coeff ;
z -> exp = temp1 -> exp ;
temp1 = temp1 -> link ;
}
else
{
if ( temp1 -> exp == temp2 -> exp )
{
z -> coeff = temp1 -> coeff + temp2 -> coeff ;
z -> exp = temp1 -> exp ;
temp1 = temp1 -> link ;
temp2 = temp2 -> link ;
}
}
}
}
while ( temp1 != NULL )
{
if ( p == NULL )
{
p = new polynode ;
z = p ;
}
else
{
z -> link = new polynode ;
z = z -> link ;
}
z -> coeff = temp1 -> coeff ;
z -> exp = temp1 -> exp ;
temp1 = temp1 -> link ;
}
while ( temp2 != NULL )
{
if ( p == NULL )
{
p = new polynode ;
z = p ;
}
else
{
z -> link = new  polynode ;
z = z -> link ;
}
z -> coeff = temp2 -> coeff ;
z -> exp = temp2 -> exp ;
temp2 = temp2 -> link ;
}
z -> link = NULL ;
}
poly :: ~poly( )
{
polynode *q ;
while ( p != NULL )
{
q = p -> link ;
delete p ;
p = q ;
}
}
void main( )
{
poly p1 ;
p1.poly_append ( 1.4, 5 ) ;
p1.poly_append ( 1.5, 4 ) ;
p1.poly_append ( 1.7, 2 ) ;
p1.poly_append ( 1.8, 1 ) ;
p1.poly_append ( 1.9, 0 ) ;
cout << "\nFirst polynomial:" ;
p1.display_poly( ) ;
poly p2 ;
p2.poly_append ( 1.5, 6 ) ;
p2.poly_append ( 2.5, 5 ) ;
p2.poly_append ( -3.5, 4 ) ;
p2.poly_append ( 4.5, 3 ) ;
p2.poly_append ( 6.5, 1 ) ;
cout << "\nSecond polynomial:" ;
p2.display_poly( ) ;
poly p3 ;
p3.poly_add ( p1, p2 ) ;
cout << "\nResultant polynomial: " ;
p3.display_poly( ) ;
}