C语言中使用链表实现多项式相加

具体步骤如下：

1. 定义一个结构体来存储一个多项式的每一项。

struct node{
    float coef;          // 系数
    int expn;            // 指数
    struct node *next;   // 指向下一个节点的指针
};

2. 定义一个函数来创建一个多项式。该函数将一个字符串作为输入，将其转换为一个多项式存储在链表中。

struct node* create(char* str){
    struct node *head, *p, *q;
    head = (struct node*)malloc(sizeof(struct node));    // 分配头节点的空间
    head->coef = 0;
    head->expn = 0;
    head->next = NULL;
    p = head;
    while(*str){
        q = (struct node*)malloc(sizeof(struct node));   // 分配新节点的空间
        q->coef = atof(str);
        while(*str != ' ') str++;   // 跳过系数部分
        q->expn = atoi(++str);
        while(*str != ' ' && *str) str++;   // 跳过指数部分
        p->next = q;
        p = q;
    }
    p->next = NULL;
    return head;
}

3. 定义一个函数来打印一个多项式。

void print(struct node* head){
    struct node *p = head->next;
    while(p){
        printf("%.2fx^%d ", p->coef, p->expn);
        p = p->next;
    }
    printf("\n");
}

4. 定义一个函数来将两个多项式相加。该函数接收两个链表指针，返回一个链表指针。

struct node* add(struct node* head1, struct node* head2){
    struct node *p = head1->next, *q = head2->next, *r, *s;
    struct node *head = (struct node*)malloc(sizeof(struct node));
    head->coef = 0;
    head->expn = 0;
    head->next = NULL;
    s = head;
    while(p && q){
        r = (struct node*)malloc(sizeof(struct node));
        if(p->expn < q->expn){
            r->coef = p->coef;
            r->expn = p->expn;
            p = p->next;
        }
        else if(p->expn > q->expn){
            r->coef = q->coef;
            r->expn = q->expn;
            q = q->next;
        }
        else{
            r->coef = p->coef + q->coef;
            r->expn = p->expn;
            p = p->next;
            q = q->next;
        }
        s->next = r;
        s = r;
    }
    while(p){
        r = (struct node*)malloc(sizeof(struct node));
        r->coef = p->coef;
        r->expn = p->expn;
        p = p->next;
        s->next = r;
        s = r;
    }
    while(q){
        r = (struct node*)malloc(sizeof(struct node));
        r->coef = q->coef;
        r->expn = q->expn;
        q = q->next;
        s->next = r;
        s = r;
    }
    s->next = NULL;
    return head;
}

5. 测试函数。

int main(){
    struct node *head1, *head2, *head3;
    char str1[50], str2[50];
    printf("请输入第一个多项式：");
    fgets(str1, 50, stdin);
    printf("请输入第二个多项式：");
    fgets(str2, 50, stdin);
    head1 = create(str1);
    head2 = create(str2);
    head3 = add(head1, head2);
    printf("第一个多项式：");
    print(head1);
    printf("第二个多项式：");
    print(head2);
    printf("相加结果：");
    print(head3);
    return 0;
}