2-1 Add Two Polynomials

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 <stdio.h>
#include <stdlib.h>
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

我的答案

Polynomial Add(Polynomial a, Polynomial b) {

    Polynomial pa, pb;
    PtrToNode p;
    Polynomial head = (Polynomial) malloc(sizeof(struct Node));
    head->Next = NULL;
    pa = a->Next;
    pb = b->Next;
    PtrToNode r = head;

    while (pa && pb) {
        if (pa->Exponent > pb->Exponent) {
            p = pa;
            pa = pa->Next;
            p->Next = NULL;
            r->Next = p;
            r = p;
        } else if (pa->Exponent < pb->Exponent) {
            p = pb;
            pb = pb->Next;
            p->Next = NULL;
            r->Next = p;
            r = p;
        } else {
            pa->Coefficient += pb->Coefficient;
            if (pa->Coefficient == 0) {
                pa = pa->Next;
                pb = pb->Next;
                continue;
            }
            p = pa;
            pa = pa->Next;
            pb = pb->Next;
            p->Next = NULL;
            r->Next = p;
            r = p;
        }
    }
    if (pa)
        r->Next = pa;
    else
        r->Next = pb;
    
    return head;
    
}

来源：https://blog.csdn.net/weixin_43728310/article/details/101073983