编写程序，对两个一元多项式求和，并输出“和多项式”。

非常感谢您的提问，以下是对两个一元多项式求和的程序：

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

#define MAX_DEGREE 100 // 多项式最大次数

struct polynomial {
    int degree;     // 多项式次数
    float coeff[MAX_DEGREE+1];  // 多项式系数
};

struct polynomial add(struct polynomial p1, struct polynomial p2);

int main() {
    struct polynomial p1, p2, result;
    int i;

    printf("Please input the degree of polynomial 1 (less than %d):\n", MAX_DEGREE);
    scanf("%d", &p1.degree);
    printf("Please input the coefficients of polynomial 1 (in descending order of degree):\n");
    for (i = 0; i <= p1.degree; i++) {
        scanf("%f", &p1.coeff[i]);
    }

    printf("Please input the degree of polynomial 2 (less than %d):\n", MAX_DEGREE);
    scanf("%d", &p2.degree);
    printf("Please input the coefficients of polynomial 2 (in descending order of degree):\n");
    for (i = 0; i <= p2.degree; i++) {
        scanf("%f", &p2.coeff[i]);
    }

    result = add(p1, p2);

    printf("The sum polynomial is:\n");
    printf("%.2fx^%d", result.coeff[result.degree], result.degree);
    for (i = result.degree-1; i >= 0; i--) {
        if (result.coeff[i] > 0) {
            printf(" + %.2fx^%d", result.coeff[i], i);
        } else if (result.coeff[i] < 0) {
            printf(" - %.2fx^%d", -result.coeff[i], i);
        }
    }
    printf("\n");

    return 0;
}

struct polynomial add(struct polynomial p1, struct polynomial p2) {
    struct polynomial result;
    int i;

    if (p1.degree >= p2.degree) {
        result.degree = p1.degree;
    } else {
        result.degree = p2.degree;
    }

    for (i = 0; i <= result.degree; i++) {
        result.coeff[i] = 0;
        if (i <= p1.degree) {
            result.coeff[i] += p1.coeff[i];
        }
        if (i <= p2.degree) {
            result.coeff[i] += p2.coeff[i];
        }
    }

    return result;
}

该程序会先让用户分别输入两个多项式的次数和系数，并对它们求和，最后输出求和后的多项式。程序中使用了一个结构体 `polynomial` 来表示多项式，同时定义了一个求和函数 `add` 。