C语言链表完成多项式的降幂输出

假设多项式的项的结构体如下所示：

typedef struct Term {
    int coef;   // 系数
    int expn;   // 指数
    struct Term *next;
} Term;

则可以按照以下步骤完成多项式的降幂输出：

1. 定义一个指针p指向多项式头节点。

2. 定义一个数组arr，用于存储多项式的每一项。

3. 遍历多项式，将每一项依次存入数组arr中。

4. 对数组arr进行降序排序。

5. 遍历数组arr，将每个元素输出。

下面是C语言代码实现：

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

typedef struct Term {
    int coef;   // 系数
    int expn;   // 指数
    struct Term *next;
} Term;

void insert(Term **head, int coef, int expn) {
    Term *new_node = (Term*)malloc(sizeof(Term));
    new_node->coef = coef;
    new_node->expn = expn;
    new_node->next = *head;
    *head = new_node;
}

void print_poly(Term *head) {
    Term *p = head;
    while (p != NULL) {
        if (p->coef > 0) {
            printf("+");
        }
        printf("%dx^%d", p->coef, p->expn);
        p = p->next;
    }
}

void print_poly_desc(Term *head) {
    Term *p = head;
    int count = 0;
    while (p != NULL) {
        count++;
        p = p->next;
    }
    Term *arr[count];
    p = head;
    int i = 0;
    while (p != NULL) {
        arr[i] = p;
        p = p->next;
        i++;
    }
    for (int j = 0; j < count; j++) {
        for (int k = j + 1; k < count; k++) {
            if (arr[j]->expn < arr[k]->expn) {
                Term *temp = arr[j];
                arr[j] = arr[k];
                arr[k] = temp;
            }
        }
        if (arr[j]->coef > 0) {
            printf("+");
        }
        printf("%dx^%d", arr[j]->coef, arr[j]->expn);
    }
}

int main() {
    Term *poly = NULL;
    insert(&poly, 3, 2);
    insert(&poly, 4, 3);
    insert(&poly, 5, 1);
    insert(&poly, 2, 4);
    printf("原始多项式：");
    print_poly(poly);
    printf("\n降幂输出：");
    print_poly_desc(poly);
    printf("\n");
    return 0;
}

输出结果为：

原始多项式:+2x^4+5x^1+4x^3+3x^2
降幂输出：+2x^4+4x^3+3x^2+5x^1