用c语言链表知识写一个学生成绩统计程序，要求能录入学生的姓名学号成绩，并依据学生平均成绩由大到小排序输出

以下是一个基于C语言链表的学生成绩统计程序：

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

// 定义学生结构体
struct student {
    char name[20];
    char id[10];
    float score;
    struct student* next;
};

// 定义链表头结点
struct student* head = NULL;

// 插入学生信息
void insert_student() {
    struct student* new_node = (struct student*)malloc(sizeof(struct student));
    printf("请输入学生姓名：");
    scanf("%s", new_node->name);
    printf("请输入学生学号：");
    scanf("%s", new_node->id);
    printf("请输入学生成绩：");
    scanf("%f", &new_node->score);

    new_node->next = head;
    head = new_node;
}

// 输出学生信息
void print_students() {
    struct student* current = head;
    while (current != NULL) {
        printf("学生姓名：%s，学号：%s，成绩：%.2f\n", current->name, current->id, current->score);
        current = current->next;
    }
}

// 计算平均成绩
float calc_avg_score() {
    float sum = 0;
    int count = 0;
    struct student* current = head;
    while (current != NULL) {
        sum += current->score;
        count++;
        current = current->next;
    }
    return sum / count;
}

// 比较函数，用于排序
int compare_scores(const void* a, const void* b) {
    struct student* s1 = *(struct student**)a;
    struct student* s2 = *(struct student**)b;
    if (s1->score < s2->score) {
        return 1;
    } else if (s1->score > s2->score) {
        return -1;
    } else {
        return 0;
    }
}

// 排序并输出
void sort_and_print_students() {
    // 将链表转换为数组
    int num_students = 0;
    struct student* current = head;
    while (current != NULL) {
        num_students++;
        current = current->next;
    }
    struct student** students_array = (struct student**)malloc(num_students * sizeof(struct student*));
    current = head;
    int i = 0;
    while (current != NULL) {
        students_array[i] = current;
        current = current->next;
        i++;
    }

    // 对数组进行排序
    qsort(students_array, num_students, sizeof(struct student*), compare_scores);

    // 输出排序后的学生信息
    printf("按平均成绩由大到小排序后的学生信息：\n");
    for (i = 0; i < num_students; i++) {
        printf("学生姓名：%s，学号：%s，成绩：%.2f\n", students_array[i]->name, students_array[i]->id, students_array[i]->score);
    }

    // 释放数组内存
    free(students_array);
}

int main() {
    int choice;
    do {
        printf("\n");
        printf("1. 插入学生信息\n");
        printf("2. 输出学生信息\n");
        printf("3. 计算平均成绩\n");
        printf("4. 按平均成绩由大到小排序并输出\n");
        printf("5. 退出程序\n");
        printf("请输入您的选择：");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                insert_student();
                break;
            case 2:
                print_students();
                break;
            case 3:
                printf("平均成绩为：%.2f\n", calc_avg_score());
                break;
            case 4:
                sort_and_print_students();
                break;
            case 5:
                printf("感谢使用本程序！\n");
                break;
            default:
                printf("无效选择，请重新输入！\n");
                break;
        }
    } while (choice != 5);

    // 释放链表内存
    struct student* current = head;
    while (current != NULL) {
        struct student* temp = current;
        current = current->next;
        free(temp);
    }

    return 0;
}

该程序使用链表存储学生信息，并提供了插入、输出、计算平均成绩、排序并输出等功能。其中，排序使用了C标准库中的快速排序函数qsort()，需要传入比较函数compare_scores()进行比较。在比较函数内部，按照学生成绩从大到小排序。最后，为了避免内存泄漏，需要在程序结束时释放链表内存。