6-3 Add Two Polynomials（20 分）

6-3 Add Two Polynomials（20 分）

Write a function to add two polynomials. Do not destroy the input. Use a linked list implementation with a dummy head node. Note: The zero polynomial is represented by an empty list with only the dummy head node.

Format of functions:

Polynomial Add( Polynomial a, Polynomial b );

where Polynomial is defined as the following:

typedef struct Node *PtrToNode;
struct Node {
    int Coefficient;
    int Exponent;
    PtrToNode Next;
};
typedef PtrToNode Polynomial;
/* Nodes are sorted in decreasing order of exponents.*/

The function Add is supposed to return a polynomial which is the sum of a and b.

Sample program of judge:

#include 
#include 
typedef struct Node *PtrToNode;
struct Node  {
    int Coefficient;
    int Exponent;
    PtrToNode Next;
};
typedef PtrToNode Polynomial;

Polynomial Read(); /* details omitted */
void Print( Polynomial p ); /* details omitted */
Polynomial Add( Polynomial a, Polynomial b );

int main()
{
    Polynomial a, b, s;
    a = Read();
    b = Read();
    s = Add(a, b);
    Print(s);
    return 0;
}

/* Your function will be put here */

Sample Input:

4
3 4 -5 2 6 1 -2 0
3
5 20 -7 4 3 1

Sample Output:

5 20 -4 4 -5 2 9 1 -2 0

Polynomial Add(Polynomial a, Polynomial b)

{
if (!a->Next) { return b; }
if (!b->Next) { return a; }
a = a->Next; b = b->Next;
Polynomial c = (Polynomial)malloc(sizeof(struct Node));
c->Coefficient = c->Exponent = 0;
c->Next = NULL;
PtrToNode p = c;
while (a && b) {
if (a->Exponent > b->Exponent) {
PtrToNode tmp = (PtrToNode)malloc(sizeof(struct Node));
tmp->Coefficient = a->Coefficient;
tmp->Exponent = a->Exponent;
tmp->Next = NULL;
p->Next = tmp;
p = p->Next;
a = a->Next;
}
else if (a->Exponent < b->Exponent) {
PtrToNode tmp = (PtrToNode)malloc(sizeof(struct Node));
tmp->Coefficient = b->Coefficient;
tmp->Exponent = b->Exponent;
tmp->Next = NULL;
p->Next = tmp;
p = p->Next;
b = b->Next;
}
else {
if (a->Coefficient + b->Coefficient != 0) {
PtrToNode tmp = (PtrToNode)malloc(sizeof(struct Node));
tmp->Coefficient = b->Coefficient + a->Coefficient;
tmp->Exponent = b->Exponent;
tmp->Next = NULL;
p->Next = tmp;
p = p->Next;
}
b = b->Next;
a = a->Next;
}
if (!a) {
while (b && b->Coefficient!=0) {
PtrToNode tmp = (PtrToNode)malloc(sizeof(struct Node));
tmp->Coefficient = b->Coefficient;
tmp->Exponent = b->Exponent;
tmp->Next = NULL;
p->Next = tmp;
p = p->Next;
b = b->Next;
}
}
if (!b) {
while (a && a->Coefficient!=0) {
PtrToNode tmp = (PtrToNode)malloc(sizeof(struct Node));
tmp->Coefficient = a->Coefficient;
tmp->Exponent = a->Exponent;
tmp->Next = NULL;
p->Next = tmp;
p = p->Next;
a = a->Next;
}
}
}
return c;
}