建立一个链表，每个节点包括：学号、姓名、性别、年龄。输入一个年龄，如果链表中有与此年龄相同的节点，则将此节点删去

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

typedef struct student {
    int id;
    char name[20];
    char gender[5];
    int age;
    struct student* next;
} Student;

Student* create_student(int id, char* name, char* gender, int age) {
    Student* new_student = (Student*)malloc(sizeof(Student));
    new_student->id = id;
    strcpy(new_student->name, name);
    strcpy(new_student->gender, gender);
    new_student->age = age;
    new_student->next = NULL;
    return new_student;
}

Student* add_student(Student* head, int id, char* name, char* gender, int age) {
    Student* new_student = create_student(id, name, gender, age);
    if (head == NULL) {
        head = new_student;
    } else {
        Student* current = head;
        while (current->next != NULL) {
            current = current->next;
        }
        current->next = new_student;
    }
    return head;
}

Student* delete_student(Student* head, int age) {
    if (head == NULL) {
        return NULL;
    }
    Student* current = head;
    Student* previous = NULL;
    while (current != NULL) {
        if (current->age == age) {
            if (previous == NULL) {
                head = current->next;
            } else {
                previous->next = current->next;
            }
            free(current);
            current = previous == NULL ? head : previous->next;
        } else {
            previous = current;
            current = current->next;
        }
    }
    return head;
}

void print_student(Student* student) {
    printf("ID: %d, Name: %s, Gender: %s, Age: %d\n", student->id, student->name, student->gender, student->age);
}

void print_all_students(Student* head) {
    if (head == NULL) {
        printf("The list is empty.\n");
    } else {
        Student* current = head;
        while (current != NULL) {
            print_student(current);
            current = current->next;
        }
    }
}

void free_all_students(Student* head) {
    Student* current = head;
    while (current != NULL) {
        Student* next = current->next;
        free(current);
        current = next;
    }
}

int main() {
    int id, age;
    char name[20], gender[5];
    Student* head = NULL;
    printf("Please enter student information (ID, Name, Gender, Age), enter -1 to stop.\n");
    while (1) {
        printf("ID: ");
        scanf("%d", &id);
        if (id == -1) {
            break;
        }
        printf("Name: ");
        scanf("%s", name);
        printf("Gender: ");
        scanf("%s", gender);
        printf("Age: ");
        scanf("%d", &age);
        head = add_student(head, id, name, gender, age);
    }
    printf("Please enter an age to delete: ");
    scanf("%d", &age);
    head = delete_student(head, age);
    printf("The remaining students are:\n");
    print_all_students(head);
    free_all_students(head);
    return 0;
}