用C语言写出，构造两个按指数递增的有序链表，实现两个一元多项式相加

在C语言中，我们可以创建一个结构体来表示多项式的项，包括系数和指数。然后，我们构建两个链表分别存储两个一元多项式，并实现一个函数来进行相加操作。这里是一个简单的示例：

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

// 定义多项式的节点结构
typedef struct {
    double coefficient; // 系数
    int exponent;       // 指数
    struct Node *next;  // 下一个节点指针
} PolynomialTerm;

typedef PolynomialTerm* PolynomialList;

// 初始化一个新的多项式节点
PolynomialTerm* createTerm(double c, int e) {
    PolynomialTerm *newTerm = (PolynomialTerm*)malloc(sizeof(PolynomialTerm));
    newTerm->coefficient = c;
    newTerm->exponent = e;
    newTerm->next = NULL;
    return newTerm;
}

// 合并两个链表，将它们按照指数递增排序
void mergeAndSortTerms(PolynomialList* headA, PolynomialList* headB, PolynomialList* result) {
    PolynomialTerm *currA = headA, *currB = headB, *prev = NULL, *temp;

    while (currA && currB) {
        if (currA->exponent < currB->exponent) {
            if (prev == NULL) {
                temp = currA;
                prev = currA;
            } else {
                temp->next = currA;
                prev = temp;
            }
            currA = currA->next;
        } else if (currA->exponent > currB->exponent) {
            if (prev == NULL) {
                temp = currB;
                prev = currB;
            } else {
                temp->next = currB;
                prev = temp;
            }
            currB = currB->next;
        } else { // 当前项的指数相同，合并系数
            double sumCoefficient = currA->coefficient + currB->coefficient;
            temp = createTerm(sumCoefficient, currA->exponent);
            prev->next = temp;
            currA = currA->next;
            currB = currB->next;
        }
    }

    // 如果其中一个链表未遍历完，添加剩余部分
    if (currA) {
        temp->next = currA;
    } else if (currB) {
        temp->next = currB;
    }

    *result = temp;
}

// 主函数，演示如何使用上述功能
int main() {
    PolynomialList list1 = NULL, list2 = NULL, mergedList = NULL;
    PolynomialTerm* termA1 = createTerm(2.0, 0);   // x^0 + 2
    PolynomialTerm* termA2 = createTerm(1.0, 1);   // x^1 + 1
    PolynomialTerm* termB1 = createTerm(3.0, -1);  // 3/x - 1

    list1 = termA1;
    list1->next = termA2;

    list2 = termB1;

    mergeAndSortTerms(&list1, &list2, &mergedList);

    // 打印结果
    PolynomialTerm* curr = mergedList;
    printf("Sorted polynomial: ");
    while (curr != NULL) {
        printf("%f*x^%d ", curr->coefficient, curr->exponent);
        curr = curr->next;
    }

    return 0;
}

在这个例子中，`mergeAndSortTerms` 函数用于合并两个已排序的链表，确保结果也是按照指数递增排列。注意这个代码假设输入的链表已经按照升序排列了指数。如果需要处理不确定的输入，可以在合并之前先对链表进行预处理。