用c语言写一个学生考勤系统，包含以下功能1、 录入学生的缺课记录。 2、 修改某个学生的缺课记录。 3、 查询某个学生的缺课情况。 统计某段时间内，旷课学生姓名及旷课次数，按旷课次数由多到少排序。

好的，我可以为您解答这个问题。

以下是一个简单的学生考勤系统的C代码，它包含了您所提到的所有功能：

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

#define MAX_STUDENTS 100
#define MAX_NAME_LENGTH 50
#define MAX_ABSENCES 20

typedef struct {
    char name[MAX_NAME_LENGTH];
    int absences[MAX_ABSENCES];
    int num_absences;
} Student;

Student students[MAX_STUDENTS];
int num_students = 0;

// Function declarations
void add_student();
void enter_absences();
void modify_absences();
void display_absences();
void display_statistics();

// Main function
int main() {
    int choice;

    do {
        // Display menu
        printf("\n\n");
        printf("1. Add student\n");
        printf("2. Enter absences\n");
        printf("3. Modify absences\n");
        printf("4. Display absences\n");
        printf("5. Display statistics\n");
        printf("6. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        // Call appropriate function based on user choice
        switch (choice) {
            case 1:
                add_student();
                break;
            case 2:
                enter_absences();
                break;
            case 3:
                modify_absences();
                break;
            case 4:
                display_absences();
                break;
            case 5:
                display_statistics();
                break;
            case 6:
                exit(0);
            default:
                printf("Invalid choice!\n");
        }
    } while (1);

    return 0;
}

// Function to add a new student
void add_student() {
    if (num_students == MAX_STUDENTS) {
        printf("Maximum number of students reached!\n");
        return;
    }

    printf("Enter name of student: ");
    scanf("%s", students[num_students].name);

    students[num_students].num_absences = 0;

    printf("Student added successfully!\n");
    num_students++;
}

// Function to enter absences for a student
void enter_absences() {
    char name[MAX_NAME_LENGTH];
    int i, j, found = 0;

    printf("Enter name of student: ");
    scanf("%s", name);

    for (i = 0; i < num_students; i++) {
        if (strcmp(name, students[i].name) == 0) {
            found = 1;
            break;
        }
    }

    if (!found) {
        printf("Student not found!\n");
        return;
    }

    printf("Enter number of absences: ");
    scanf("%d", &students[i].num_absences);

    printf("Enter dates of absences (separated by spaces): ");
    for (j = 0; j < students[i].num_absences; j++) {
        scanf("%d", &students[i].absences[j]);
    }

    printf("Absences entered successfully!\n");
}

// Function to modify absences for a student
void modify_absences() {
    char name[MAX_NAME_LENGTH];
    int i, j, found = 0;

    printf("Enter name of student: ");
    scanf("%s", name);

    for (i = 0; i < num_students; i++) {
        if (strcmp(name, students[i].name) == 0) {
            found = 1;
            break;
        }
    }

    if (!found) {
        printf("Student not found!\n");
        return;
    }

    printf("Enter index of absence to modify: ");
    scanf("%d", &j);

    if (j < 0 || j >= students[i].num_absences) {
        printf("Invalid index!\n");
        return;
    }

    printf("Enter new date for absence: ");
    scanf("%d", &students[i].absences[j]);

    printf("Absence modified successfully!\n");
}

// Function to display absences for a student
void display_absences() {
    char name[MAX_NAME_LENGTH];
    int i, j, found = 0;

    printf("Enter name of student: ");
    scanf("%s", name);

    for (i = 0; i < num_students; i++) {
        if (strcmp(name, students[i].name) == 0) {
            found = 1;
            break;
        }
    }

    if (!found) {
        printf("Student not found!\n");
        return;
    }

    printf("Absences for %s:\n", students[i].name);
    for (j = 0; j < students[i].num_absences; j++) {
        printf("%d\n", students[i].absences[j]);
    }
}

// Function to display statistics
void display_statistics() {
    int i, j, k, l, sum, max_sum, max_index;
    int num_absences[num_students];
    char absent_students[num_students][MAX_NAME_LENGTH];

    if (num_students == 0) {
        printf("No students added yet!\n");
        return;
    }

    for (i = 0; i < num_students; i++) {
        sum = 0;
        for (j = 0; j < students[i].num_absences; j++) {
            sum += students[i].absences[j];
        }
        num_absences[i] = sum;
        strcpy(absent_students[i], students[i].name);
    }

    printf("Enter start and end dates (inclusive): ");
    scanf("%d %d", &k, &l);

    printf("Absent students:\n");
    for (i = 0; i < num_students; i++) {
        sum = 0;
        for (j = 0; j < students[i].num_absences; j++) {
            if (students[i].absences[j] >= k && students[i].absences[j] <= l) {
                sum++;
            }
        }
        num_absences[i] = sum;
    }

    for (i = 0; i < num_students - 1; i++) {
        max_sum = num_absences[i];
        max_index = i;
        for (j = i + 1; j < num_students; j++) {
            if (num_absences[j] > max_sum) {
                max_sum = num_absences[j];
                max_index = j;
            }
        }
        if (max_index != i) {
            sum = num_absences[i];
            num_absences[i] = num_absences[max_index];
            num_absences[max_index] = sum;
            strcpy(name, absent_students[i]);
            strcpy(absent_students[i], absent_students[max_index]);
            strcpy(absent_students[max_index], name);
        }
    }

    for (i = 0; i < num_students; i++) {
        printf("%s: %d\n", absent_students[i], num_absences[i]);
    }
}

这是一个基本的学生考勤系统，它可以添加学生、录入缺课记录、修改缺课记录、查询缺课情况以及统计缺课情况。

希望我写的代码能对您有所帮助！