使用c语言书写一个成绩排序程序，要求读入数据以及输出数据均以文件形式，计算每个学生三门功课的平均分，并按平均分排列名次，若平均分相同则名次并列；结果写入文件。 3、统计全班每门课程的平均分，并计算各分数段（60以下，60~69，70~79，80~89，90以上）的学生人数；结果写入文件。 4、按格式在屏幕上打印每名学生成绩条。 5、在屏幕上打印出所有不及格学生的下列信息：学号，姓名，不及格的课程名，该不及格课程成绩。 6、在屏幕打印优等生名单（学号，姓名，三门课程成绩，平均成绩，名次），优等生必须满足下列条件： 1）平均成绩大于90分；或平均分大于85分且至少有一门功课为100分；或者平均分大于85分且至少两门课程成绩为95分以上； 2）名次在前三名； 3）每门功课及格以上。，同时要求运行时有菜单

很高兴为您解答这道题目，以下是 C 语言的代码，其中使用了结构体和链表来存储学生信息和成绩信息，并实现了菜单功能。

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

#define FILE_NAME "scores.txt"

typedef struct Student {
    char id[20];
    char name[20];
    int score1;
    int score2;
    int score3;
    double avgScore;
    int rank;
    struct Student* next;
} Student;

Student* readStudentsFromFile(char* fileName);
void writeStudentsToFile(Student* head, char* fileName);
void printStudent(Student* student);
void printStudents(Student* head);
void sortStudentsByAvgScore(Student* head);
void calculateRank(Student* head);
void calculateCourseAvgScore(Student* head, double* avg1, double* avg2, double* avg3);
void printCourseStatistics(Student* head);
void printFailedStudents(Student* head);
void printExcellentStudents(Student* head);

int main() {
    printf("Welcome to the score management system!\n");
    Student* head = readStudentsFromFile(FILE_NAME);
    if (!head) {
        printf("Failed to read data from file, program exits.\n");
        return -1;
    }
    printf("Data loaded successfully from file.\n");
    while (1) {
        printf("\nPlease select an operation:\n");
        printf("1. Print all students' scores.\n");
        printf("2. Print course statistics.\n");
        printf("3. Print failed students.\n");
        printf("4. Print excellent students.\n");
        printf("5. Exit.\n");
        int choice;
        scanf("%d", &choice);
        switch (choice) {
            case 1:
                printStudents(head);
                break;
            case 2: {
                double avg1, avg2, avg3;
                calculateCourseAvgScore(head, &avg1, &avg2, &avg3);
                printf("Course 1 average score: %.2lf\n", avg1);
                printf("Course 2 average score: %.2lf\n", avg2);
                printf("Course 3 average score: %.2lf\n", avg3);
                printCourseStatistics(head);
                break;
            }
            case 3:
                printFailedStudents(head);
                break;
            case 4:
                printExcellentStudents(head);
                break;
            case 5:
                writeStudentsToFile(head, FILE_NAME);
                printf("Data saved to file and program exits.\n");
                return 0;
            default:
                printf("Invalid choice, please try again.\n");
        }
    }
}

Student* readStudentsFromFile(char* fileName) {
    FILE* fp = fopen(fileName, "r");
    if (!fp) {
        printf("Failed to open file %s.\n", fileName);
        return NULL;
    }
    Student* head = NULL, * tail = NULL;
    while (1) {
        char id[20], name[20];
        int score1, score2, score3;
        int count = fscanf(fp, "%s %s %d %d %d", id, name, &score1, &score2, &score3);
        if (count == EOF) {
            break;
        }
        if (count != 5) {
            printf("Invalid data in file %s, program exits.\n", fileName);
            fclose(fp);
            return NULL;
        }
        Student* student = (Student*)malloc(sizeof(Student));
        strcpy(student->id, id);
        strcpy(student->name, name);
        student->score1 = score1;
        student->score2 = score2;
        student->score3 = score3;
        student->avgScore = (score1 + score2 + score3) / 3.0;
        student->next = NULL;
        if (!head) {
            head = tail = student;
        } else {
            tail->next = student;
            tail = student;
        }
    }
    fclose(fp);
    sortStudentsByAvgScore(head);
    calculateRank(head);
    return head;
}

void writeStudentsToFile(Student* head, char* fileName) {
    FILE* fp = fopen(fileName, "w");
    if (!fp) {
        printf("Failed to open file %s.\n", fileName);
        return;
    }
    Student* ptr = head;
    while (ptr) {
        fprintf(fp, "%s %s %d %d %d\n", ptr->id, ptr->name, ptr->score1, ptr->score2, ptr->score3);
        ptr = ptr->next;
    }
    fclose(fp);
}

void printStudent(Student* student) {
    printf("%s\t%s\t%d\t%d\t%d\t%.2lf\t%d\n", student->id, student->name, student->score1, student->score2, student->score3, student->avgScore, student->rank);
}

void printStudents(Student* head) {
    printf("ID\tName\tCourse 1\tCourse 2\tCourse 3\tAverage\tRank\n");
    Student* ptr = head;
    while (ptr) {
        printStudent(ptr);
        ptr = ptr->next;
    }
}

void sortStudentsByAvgScore(Student* head) {
    int count = 0;
    Student* ptr = head;
    while (ptr) {
        count++;
        ptr = ptr->next;
    }
    for (int i = 0; i < count - 1; i++) {
        ptr = head;
        for (int j = 0; j < count - i - 1; j++) {
            if (ptr->avgScore < ptr->next->avgScore) {
                char tempId[20], tempName[20];
                int tempScore1, tempScore2, tempScore3, tempRank;
                double tempAvgScore;
                strcpy(tempId, ptr->id);
                strcpy(tempName, ptr->name);
                tempScore1 = ptr->score1;
                tempScore2 = ptr->score2;
                tempScore3 = ptr->score3;
                tempAvgScore = ptr->avgScore;
                tempRank = ptr->rank;
                strcpy(ptr->id, ptr->next->id);
                strcpy(ptr->name, ptr->next->name);
                ptr->score1 = ptr->next->score1;
                ptr->score2 = ptr->next->score2;
                ptr->score3 = ptr->next->score3;
                ptr->avgScore = ptr->next->avgScore;
                ptr->rank = ptr->next->rank;
                strcpy(ptr->next->id, tempId);
                strcpy(ptr->next->name, tempName);
                ptr->next->score1 = tempScore1;
                ptr->next->score2 = tempScore2;
                ptr->next->score3 = tempScore3;
                ptr->next->avgScore = tempAvgScore;
                ptr->next->rank = tempRank;
            }
            ptr = ptr->next;
        }
    }
}

void calculateRank(Student* head) {
    int rank = 1, count = 0;
    double lastAvgScore = -1;
    Student* ptr = head;
    while (ptr) {
        count++;
        if (ptr->avgScore != lastAvgScore) {
            rank = count;
        }
        ptr->rank = rank;
        lastAvgScore = ptr->avgScore;
        ptr = ptr->next;
    }
}

void calculateCourseAvgScore(Student* head, double* avg1, double* avg2, double* avg3) {
    double sum1 = 0, sum2 = 0, sum3 = 0;
    int count = 0;
    Student* ptr = head;
    while (ptr) {
        sum1 += ptr->score1;
        sum2 += ptr->score2;
        sum3 += ptr->score3;
        count++;
        ptr = ptr->next;
    }
    *avg1 = sum1 / count;
    *avg2 = sum2 / count;
    *avg3 = sum3 / count;
}

void printCourseStatistics(Student* head) {
    int count1 = 0, count2 = 0, count3 = 0, count4 = 0, count5 = 0;
    Student* ptr = head;
    while (ptr) {
        if (ptr->score1 < 60 || ptr->score2 < 60 || ptr->score3 < 60) {
            count1++;
        } else if (ptr->avgScore < 70) {
            count2++;
        } else if (ptr->avgScore < 80) {
            count3++;
        } else if (ptr->avgScore < 90) {
            count4++;
        } else {
            count5++;
        }
        ptr = ptr->next;
    }
    printf("60 or below: %d students\n", count1);
    printf("60 - 69: %d students\n", count2);
    printf("70 - 79: %d students\n", count3);
    printf("80 - 89: %d students\n", count4);
    printf("90 or above: %d students\n", count5);
}

void printFailedStudents(Student* head) {
    printf("Failed students:\n");
    printf("ID\tName\tCourse\tScore\n");
    Student* ptr = head;
    while (ptr) {
        if (ptr->score1 < 60) {
            printf("%s\t%s\tCourse 1\t%d\n", ptr->id, ptr->name, ptr->score1);
        }
        if (ptr->score2 < 60) {
            printf("%s\t%s\tCourse 2\t%d\n", ptr->id, ptr->name, ptr->score2);
        }
        if (ptr->score3 < 60) {
            printf("%s\t%s\tCourse 3\t%d\n", ptr->id, ptr->name, ptr->score3);
        }
        ptr = ptr->next;
    }
}

void printExcellentStudents(Student* head) {
    printf("Excellent students:\n");
    printf("ID\tName\tCourse 1\tCourse 2\tCourse 3\tAverage\tRank\n");
    Student* ptr = head;
    while (ptr) {
        if (ptr->avgScore >= 90 ||
            (ptr->avgScore >= 85 && (ptr->score1 == 100 || ptr->score2 == 100 || ptr->score3 == 100)) ||
            (ptr->avgScore >= 85 && (ptr->score1 >= 95 && ptr->score2 >= 95 || ptr->score1 >= 95 && ptr->score3 >= 95 || ptr->score2 >= 95 && ptr->score3 >= 95))) {
            printStudent(ptr);
        }
        ptr = ptr->next;
    }
}

在代码中，`Student` 结构体用于存储学生信息，包括学号、姓名、三门功课成绩、平均分和排名，`next` 指针用于链接链表。`readStudentsFromFile` 函数从文件中读取学生信息，返回链表头指针；`writeStudentsToFile` 函数将链表中的学生信息写入文件；`printStudent` 函数打印一名学生的所有信息；`printStudents` 函数打印所有学生的信息；`sortStudentsByAvgScore` 函数按平均分排序所有学生；`calculateRank` 函数计算每名学生的排名；`calculateCourseAvgScore` 函数计算每门课程的平均分；`printCourseStatistics` 函数打印各分数段学生人数；`printFailedStudents` 函数打印不及格学生信息；`printExcellentStudents` 函数打印优等生信息。

在 `main` 函数中，使用 `while` 循环实现菜单功能，不断读取用户输入的操作选项，并调用相应的函数。