///////    File: Poly.C    ///////
#include <iostream.h>
#include "Poly.h"

Poly::Poly(const int *p, int n)       // p supplies n terms
: pol( n > 0 ? new int[*p+2]          // initialize pointer pol
             : new int )
{   if ( n == 0 )
        *pol = -1;                    // zero polynomial
    else
        s_to_d(pol, p);               // converted data in pol
}

// sparse-to-dense conversion, a private member
void Poly::s_to_d(int *buf, const int *p)
{    int d = *buf++ = *p;        // degree
     while ( d >= 0 )            // conversion loop
     {   if ( d == *p )
         {  *buf++ = *++p; p++;} // nonzero term
         else /* ( d > *p ) */
         {  *buf++ = 0;   }      // zero term
         d--;
     }
}

Poly Poly::operator+(Poly q)
{ int *c, *a, *b;
  Poly ans;                              // result object
  int d = deg(), dq = q.deg();
     if ( d < dq )
     {  dq = d;   d = q.deg();
        b  = pol; a = q.pol;             // d=deg(a) >= deg(b)
     }
     else
     {  a = pol;  b = q.pol;  }
     a++;  b++;
     while ( d == dq && d > 0 
                  && *a + *b == 0 )      // leading terms cancel
     {  d--;  dq--;  a++;  b++; 
     }
     ans.pol = c = new(int[d+2]);        // allocate space for result 
     *c++ = d;                           // degree of result
     while(d-- > dq) *c++ = *a++;        // leading terms
     while(d-- > -2) *c++ = *a++ + *b++; // add terms
     return(ans);
}

void Poly::display()
{ int *p = pol + 1;
  int d = deg(), e = d;
     if ( e == 0 )
     {   cout << *p << endl;
         return;
     }
     cout << '(';
     while ( d >= 0 )
     {    if ( *p !=  0 )
          {  if ( d < e ) cout << ", ";
             cout << d << "  " << *p;
          }
          d--; p++;
     }
     cout << ")\n";
}