c语言编写数据结构的一元多项式计算器，输入多项式，序列按指数升序排列，实现两个多项式的相加相减相乘，并输出相加相减相乘结果

好的，我可以帮你解答这个问题。首先，我们需要定义多项式的结构体，包含系数和指数两个成员变量：

typedef struct PolyNode {
    float coef;     // 系数
    int expn;       // 指数
    struct PolyNode *next;
} PolyNode, *Polynomial;

接着，我们可以实现多项式的输入函数，按照指数升序排列：

Polynomial CreatePoly() {
    Polynomial head = (Polynomial)malloc(sizeof(PolyNode));
    head->next = NULL;
    Polynomial p = head;
    int n;
    printf("请输入多项式项数：");
    scanf("%d", &n);
    printf("请按指数升序输入各项系数和指数，如：a*x^b\n");
    for (int i = 0; i < n; i++) {
        Polynomial node = (Polynomial)malloc(sizeof(PolyNode));
        scanf("%f*x^%d", &node->coef, &node->expn);
        while (p->next && p->next->expn <= node->expn) {
            if (p->next->expn == node->expn) {
                p->next->coef += node->coef;
                free(node);
                node = NULL;
                break;
            }
            p = p->next;
        }
        if (node) {
            node->next = p->next;
            p->next = node;
            p = head;
        }
    }
    return head;
}

接下来，我们可以实现多项式的加减乘运算，具体实现可以参考下面的代码：

Polynomial Add(Polynomial P1, Polynomial P2) {
    Polynomial head = (Polynomial)malloc(sizeof(PolyNode));
    head->next = NULL;
    Polynomial p = head;
    Polynomial p1 = P1->next, p2 = P2->next;
    while (p1 && p2) {
        if (p1->expn < p2->expn) {
            p->next = p1;
            p1 = p1->next;
        } else if (p1->expn > p2->expn) {
            p->next = p2;
            p2 = p2->next;
        } else {
            float sum = p1->coef + p2->coef;
            if (sum != 0) {
                Polynomial node = (Polynomial)malloc(sizeof(PolyNode));
                node->coef = sum;
                node->expn = p1->expn;
                p->next = node;
                p = p->next;
            }
            p1 = p1->next;
            p2 = p2->next;
        }
    }
    p->next = p1 ? p1 : p2;
    return head;
}

Polynomial Subtract(Polynomial P1, Polynomial P2) {
    Polynomial head = (Polynomial)malloc(sizeof(PolyNode));
    head->next = NULL;
    Polynomial p = head;
    Polynomial p1 = P1->next, p2 = P2->next;
    while (p1 && p2) {
        if (p1->expn < p2->expn) {
            p->next = p1;
            p1 = p1->next;
        } else if (p1->expn > p2->expn) {
            Polynomial node = (Polynomial)malloc(sizeof(PolyNode));
            node->coef = -p2->coef;
            node->expn = p2->expn;
            p->next = node;
            p = p->next;
            p2 = p2->next;
        } else {
            float diff = p1->coef - p2->coef;
            if (diff != 0) {
                Polynomial node = (Polynomial)malloc(sizeof(PolyNode));
                node->coef = diff;
                node->expn = p1->expn;
                p->next = node;
                p = p->next;
            }
            p1 = p1->next;
            p2 = p2->next;
        }
    }
    while (p1) {
        p->next = p1;
        p1 = p1->next;
        p = p->next;
    }
    while (p2) {
        Polynomial node = (Polynomial)malloc(sizeof(PolyNode));
        node->coef = -p2->coef;
        node->expn = p2->expn;
        p->next = node;
        p = p->next;
        p2 = p2->next;
    }
    return head;
}

Polynomial Multiply(Polynomial P1, Polynomial P2) {
    Polynomial head = (Polynomial)malloc(sizeof(PolyNode));
    head->next = NULL;
    Polynomial p = head;
    for (Polynomial p1 = P1->next; p1; p1 = p1->next) {
        for (Polynomial p2 = P2->next; p2; p2 = p2->next) {
            int expn = p1->expn + p2->expn;
            float coef = p1->coef * p2->coef;
            Polynomial node = (Polynomial)malloc(sizeof(PolyNode));
            node->coef = coef;
            node->expn = expn;
            while (p->next && p->next->expn <= expn) {
                if (p->next->expn == expn) {
                    p->next->coef += coef;
                    free(node);
                    node = NULL;
                    break;
                }
                p = p->next;
            }
            if (node) {
                node->next = p->next;
                p->next = node;
                p = head;
            }
        }
    }
    return head;
}

最后，我们可以在主函数中调用上述函数实现多项式的输入和运算，并输出结果：

int main() {
    Polynomial P1, P2, P;
    printf("请输入第一个多项式：\n");
    P1 = CreatePoly();
    printf("请输入第二个多项式：\n");
    P2 = CreatePoly();
    P = Add(P1, P2);
    printf("相加结果为：\n");
    PrintPoly(P);
    P = Subtract(P1, P2);
    printf("相减结果为：\n");
    PrintPoly(P);
    P = Multiply(P1, P2);
    printf("相乘结果为：\n");
    PrintPoly(P);
    return 0;
}

其中，PrintPoly函数可以用于输出多项式：

void PrintPoly(Polynomial P) {
    if (!P->next) {
        printf("0\n");
        return;
    }
    for (Polynomial p = P->next; p; p = p->next) {
        if (p->coef > 0 && p != P->next) {
            printf("+");
        }
        if (p->expn == 0) {
            printf("%.2f", p->coef);
        } else if (p->expn == 1) {
            printf("%.2f*x", p->coef);
        } else {
            printf("%.2f*x^%d", p->coef, p->expn);
        }
    }
    printf("\n");
}

这样，我们就完成了一个简单的多项式计算器。