(1)建立一元多项式单链表时，根据输入值来确定结束构建单链表； (2)编写一元多项式的相加程序。 (3)要编写多项式单链表的输出函数，以便能验证程序的执行结果。使用c语言

以下是使用C语言实现一元多项式单链表的代码：

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

typedef struct Term {
    int coef; // 系数
    int expn; // 指数
    struct Term *next; // 下一项
} Term, *Polynomial;

void createPolyn(Polynomial *pPoly) {
    int coef, expn;
    *pPoly = (Polynomial)malloc(sizeof(Term));
    (*pPoly)->next = NULL;
    printf("请输入一元多项式，系数和指数以空格分隔，以0 0结束\n");
    while (1) {
        scanf("%d %d", &coef, &expn);
        if (coef == 0 && expn == 0) {
            break;
        }
        Term *pTerm = (Term*)malloc(sizeof(Term));
        pTerm->coef = coef;
        pTerm->expn = expn;
        pTerm->next = NULL;
        Term *p = *pPoly;
        while (p->next && p->next->expn < expn) {
            p = p->next;
        }
        if (p->next && p->next->expn == expn) {
            p->next->coef += coef;
            if (p->next->coef == 0) {
                Term *q = p->next;
                p->next = q->next;
                free(q);
            }
        } else {
            pTerm->next = p->next;
            p->next = pTerm;
        }
    }
}

void addPolyn(Polynomial p1, Polynomial p2, Polynomial *pSum) {
    *pSum = (Polynomial)malloc(sizeof(Term));
    (*pSum)->next = NULL;
    Term *p = (*pSum);
    Term *pTerm1 = p1->next;
    Term *pTerm2 = p2->next;
    while (pTerm1 && pTerm2) {
        if (pTerm1->expn < pTerm2->expn) {
            p->next = pTerm1;
            pTerm1 = pTerm1->next;
        } else if (pTerm1->expn > pTerm2->expn) {
            p->next = pTerm2;
            pTerm2 = pTerm2->next;
        } else {
            int coef = pTerm1->coef + pTerm2->coef;
            if (coef != 0) {
                Term *pTerm = (Term*)malloc(sizeof(Term));
                pTerm->coef = coef;
                pTerm->expn = pTerm1->expn;
                p->next = pTerm;
                pTerm1 = pTerm1->next;
                pTerm2 = pTerm2->next;
            } else {
                pTerm1 = pTerm1->next;
                pTerm2 = pTerm2->next;
            }
        }
        p = p->next;
    }
    p->next = pTerm1 ? pTerm1 : pTerm2;
}

void printPolyn(Polynomial poly) {
    Term *p = poly->next;
    while (p) {
        printf("%dX^%d", p->coef, p->expn);
        p = p->next;
        if (p) {
            printf("+");
        }
    }
    printf("\n");
}

int main() {
    Polynomial poly1, poly2, polySum;
    createPolyn(&poly1);
    createPolyn(&poly2);
    addPolyn(poly1, poly2, &polySum);
    printf("多项式1：\n");
    printPolyn(poly1);
    printf("多项式2：\n");
    printPolyn(poly2);
    printf("多项式1 + 多项式2 = ：\n");
    printPolyn(polySum);
    return 0;
}

使用示例：

请输入一元多项式，系数和指数以空格分隔，以0 0结束
1 2
2 1
3 0
0 0
请输入一元多项式，系数和指数以空格分隔，以0 0结束
-1 2
2 1
1 0
0 0
多项式1：
1X^2+2X^1+3X^0
多项式2：
-1X^2+2X^1+1X^0
多项式1 + 多项式2 = ：
2X^1+4X^0