c语言实现 问题描述:给出n个学生的考试成绩表，成绩表包括学生的学号、姓名、考试成绩(高等数学、英语、物理)，设计一个简单的成绩管理程序。基本要求:(1)建立成绩表，能够插入、删除、修改学生的成绩记录; (2)按任一单科成绩排序; (3)计算每名学生的平均成绩; 4)根据平均成绩将成绩表按由高到低的次序排列,统计每名学生在考试中获得的名次，分数相同的为同一名次，按名次输出成绩表。提高要求:以文件形式保存成绩表，可以从文件读取数据。

以下是一个简单的C语言实现，实现了上述基本要求：

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

#define MAX_STUDENT_NUM 100

struct student {
    char id[20];
    char name[20];
    int math_grade;
    int english_grade;
    int physics_grade;
    float avg_grade;
    int rank;
};

struct student students[MAX_STUDENT_NUM];
int student_num = 0;

void print_menu() {
    printf("1. 添加学生\n");
    printf("2. 删除学生\n");
    printf("3. 修改学生信息\n");
    printf("4. 按单科成绩排序\n");
    printf("5. 计算平均成绩并按排名输出\n");
    printf("6. 从文件读取数据\n");
    printf("7. 保存数据到文件\n");
    printf("8. 退出\n");
}

void add_student() {
    if (student_num >= MAX_STUDENT_NUM) {
        printf("学生数量已达上限\n");
        return;
    }

    struct student s;
    printf("请输入学号：");
    scanf("%s", s.id);
    printf("请输入姓名：");
    scanf("%s", s.name);
    printf("请输入高数成绩：");
    scanf("%d", &s.math_grade);
    printf("请输入英语成绩：");
    scanf("%d", &s.english_grade);
    printf("请输入物理成绩：");
    scanf("%d", &s.physics_grade);

    s.avg_grade = (s.math_grade + s.english_grade + s.physics_grade) / 3.0;
    s.rank = 0;

    students[student_num++] = s;
    printf("添加成功\n");
}

void delete_student() {
    char id[20];
    printf("请输入要删除的学生的学号：");
    scanf("%s", id);

    int i;
    for (i = 0; i < student_num; i++) {
        if (strcmp(students[i].id, id) == 0) {
            break;
        }
    }

    if (i == student_num) {
        printf("未找到该学生\n");
        return;
    }

    for (int j = i; j < student_num - 1; j++) {
        students[j] = students[j + 1];
    }

    student_num--;
    printf("删除成功\n");
}

void modify_student() {
    char id[20];
    printf("请输入要修改的学生的学号：");
    scanf("%s", id);

    int i;
    for (i = 0; i < student_num; i++) {
        if (strcmp(students[i].id, id) == 0) {
            break;
        }
    }

    if (i == student_num) {
        printf("未找到该学生\n");
        return;
    }

    struct student s;
    printf("请输入新的高数成绩：");
    scanf("%d", &s.math_grade);
    printf("请输入新的英语成绩：");
    scanf("%d", &s.english_grade);
    printf("请输入新的物理成绩：");
    scanf("%d", &s.physics_grade);

    s.avg_grade = (s.math_grade + s.english_grade + s.physics_grade) / 3.0;
    s.rank = 0;

    students[i] = s;
    printf("修改成功\n");
}

int cmp_math_grade(const void *a, const void *b) {
    return ((struct student *) b)->math_grade - ((struct student *) a)->math_grade;
}

int cmp_english_grade(const void *a, const void *b) {
    return ((struct student *) b)->english_grade - ((struct student *) a)->english_grade;
}

int cmp_physics_grade(const void *a, const void *b) {
    return ((struct student *) b)->physics_grade - ((struct student *) a)->physics_grade;
}

void sort_by_grade() {
    int choice;
    printf("请选择排序方式：\n");
    printf("1. 按高数成绩排序\n");
    printf("2. 按英语成绩排序\n");
    printf("3. 按物理成绩排序\n");
    scanf("%d", &choice);

    switch (choice) {
        case 1:
            qsort(students, student_num, sizeof(struct student), cmp_math_grade);
            printf("按高数成绩排序成功\n");
            break;
        case 2:
            qsort(students, student_num, sizeof(struct student), cmp_english_grade);
            printf("按英语成绩排序成功\n");
            break;
        case 3:
            qsort(students, student_num, sizeof(struct student), cmp_physics_grade);
            printf("按物理成绩排序成功\n");
            break;
        default:
            printf("无效的选择\n");
    }
}

int cmp_avg_grade(const void *a, const void *b) {
    if (((struct student *) b)->avg_grade > ((struct student *) a)->avg_grade) {
        return 1;
    } else if (((struct student *) b)->avg_grade < ((struct student *) a)->avg_grade) {
        return -1;
    } else {
        return 0;
    }
}

void calculate_rank() {
    qsort(students, student_num, sizeof(struct student), cmp_avg_grade);

    int rank = 1;
    for (int i = 0; i < student_num; i++) {
        if (i > 0 && students[i].avg_grade != students[i - 1].avg_grade) {
            rank = i + 1;
        }
        students[i].rank = rank;
    }

    printf("计算排名成功\n");
}

void print_students() {
    printf("学号\t姓名\t高数成绩\t英语成绩\t物理成绩\t平均成绩\t排名\n");
    for (int i = 0; i < student_num; i++) {
        printf("%s\t%s\t%d\t\t%d\t\t%d\t\t%.2f\t\t%d\n", students[i].id, students[i].name,
               students[i].math_grade, students[i].english_grade, students[i].physics_grade,
               students[i].avg_grade, students[i].rank);
    }
}

void load_data() {
    FILE *fp = fopen("students.txt", "r");
    if (fp == NULL) {
        printf("无法打开文件\n");
        return;
    }

    char id[20], name[20];
    int math_grade, english_grade, physics_grade;

    while (fscanf(fp, "%s %s %d %d %d", id, name, &math_grade, &english_grade, &physics_grade) == 5) {
        struct student s;
        strcpy(s.id, id);
        strcpy(s.name, name);
        s.math_grade = math_grade;
        s.english_grade = english_grade;
        s.physics_grade = physics_grade;
        s.avg_grade = (math_grade + english_grade + physics_grade) / 3.0;
        s.rank = 0;
        students[student_num++] = s;
    }

    fclose(fp);
    printf("从文件读取数据成功\n");
}

void save_data() {
    FILE *fp = fopen("students.txt", "w");
    if (fp == NULL) {
        printf("无法打开文件\n");
        return;
    }

    for (int i = 0; i < student_num; i++) {
        fprintf(fp, "%s %s %d %d %d\n", students[i].id, students[i].name,
                students[i].math_grade, students[i].english_grade, students[i].physics_grade);
    }

    fclose(fp);
    printf("保存数据到文件成功\n");
}

int main() {
    int choice;

    while (1) {
        print_menu();
        printf("请选择操作：");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                add_student();
                break;
            case 2:
                delete_student();
                break;
            case 3:
                modify_student();
                break;
            case 4:
                sort_by_grade();
                break;
            case 5:
                calculate_rank();
                print_students();
                break;
            case 6:
                load_data();
                break;
            case 7:
                save_data();
                break;
            case 8:
                exit(0);
            default:
                printf("无效的选择\n");
        }

        printf("\n");
    }
}

注意，这只是一个简单的实现，可能存在一些局限性和bug，可以根据实际需求进行扩展和改进。