c语言 求两个多项式的乘积（1）编写函数实现一个多项式的输入，返回多项式链表的头指针。（2）编写函数实现两个多项式相乘，返回结果多项式链表的头指针。（3）编写函数输出一个多项式的二元组序列。（4）在main函数中分别调用上述函数，实现输入两个多项式，求出它们的乘积并输出结果，先输入多项式非零项的个数，再输入每一对非零项系数和指。输出结果为乘积多项式的非零项的个数和每一对非零项系数和指数。系数和指数均为整数

下面是对应的C语言代码：

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

typedef struct node {
    int coef;   // 系数
    int expn;   // 指数
    struct node *next;  // 指向下一个结点的指针
} PolyNode, *PolyLink;

// 输入一个多项式
PolyLink createPoly() {
    PolyLink head, tail, p;
    int n, coef, expn;
    scanf("%d", &n);
    head = tail = (PolyLink)malloc(sizeof(PolyNode));
    head->next = NULL;
    while (n--) {
        scanf("%d %d", &coef, &expn);
        p = (PolyLink)malloc(sizeof(PolyNode));
        p->coef = coef;
        p->expn = expn;
        tail->next = p;
        tail = p;
    }
    tail->next = NULL;
    return head;
}

// 两个多项式相乘
PolyLink multiplyPoly(PolyLink A, PolyLink B) {
    PolyLink head, tail, p, q, r;
    int coef, expn;
    head = tail = (PolyLink)malloc(sizeof(PolyNode));
    head->next = NULL;
    for (p = A->next; p != NULL; p = p->next) {
        for (q = B->next; q != NULL; q = q->next) {
            coef = p->coef * q->coef;
            expn = p->expn + q->expn;
            for (r = head->next; r != NULL; r = r->next) {
                if (r->expn == expn) {
                    r->coef += coef;
                    break;
                }
            }
            if (r == NULL) {
                r = (PolyLink)malloc(sizeof(PolyNode));
                r->coef = coef;
                r->expn = expn;
                r->next = head->next;
                head->next = r;
            }
        }
    }
    return head;
}

// 输出一个多项式
void printPoly(PolyLink poly) {
    PolyLink p;
    for (p = poly->next; p != NULL; p = p->next) {
        printf("(%d,%d)", p->coef, p->expn);
        if (p->next != NULL) {
            printf(",");
        }
    }
    printf("\n");
}

int main() {
    PolyLink A, B, C;
    A = createPoly();
    B = createPoly();
    C = multiplyPoly(A, B);
    printPoly(C);
    return 0;
}

注意：该代码中假设多项式的指数都是非负整数。如果需要处理负指数的情况，需要对代码进行修改。