链接列表插入和删除不适用于相同的 id

Question

我正在尝试编写一些函数，您可以在其中插入一个学生（姓名，身份证）到列表中并删除他。如果学生已经在列表中，我删除了他，然后尝试再次插入他，程序输出：Student added successfuly 但他没有出现在列表中。当我再次运行程序并尝试插入他（这次他不存在于列表中）时，程序运行正常。请注意，所有内容均基于学生的 id 而不是他的姓名。以下是函数：

int addStudent(student st, list l){

    if (findStudent(st->id, l) == NULL)
    {
        list_push_back(l, st->name, st->id);
        return 1;
    }

    return 0;
}

student findStudent(int id, list l){
    student stTemp = l->head;

    if (l->size != 0)
    {
        while (stTemp != NULL)
        {
            if (stTemp->id == id)//check if the student's id is the same as the student's id in the struct
            {
                return stTemp;
            }
            stTemp = stTemp->next; 
        }

    }

    return NULL;
}

list list_push_back(list l, char *name, int id)
{
    student new_student = malloc(sizeof(struct studentR));
    if (new_student == NULL)
    {
        printf("Error allocating memory\n");
        abort();
    }


    strcpy(new_student->name, name);
    new_student->id = id;
    new_student->next = NULL;

    if (list_isempty(l))
    {
        l->head = new_student;
    }
    else
    {
        l->tail->next = new_student;
    }
    l->tail = new_student;
    l->size++;

    return l;
}

int deleteStudent(student st, list l){
    //check if the list is empty
    if (list_isempty(l))
    {
        return 0;
    }

    //check if the student is in the list
    st = findStudent(st->id, l);
    if (st == NULL)
    {
        return 0;
    }

    student temp = l->head;
    student prev = temp;    
    //if student to be deleted is the first in the list
    if (l->head->id == st->id)
    {
        l->head = temp->next;
        free(temp);
        l->size--;

        return 1;
    }

    //if student to be deleted is the last in the list
    if (l->tail == st->next)
    {
        while (temp->id != st->id)
        {
            prev = temp;
            temp = temp->next;
        }
        prev->next = NULL;
        l->tail = prev;
        free(temp);
        l->size--;

        return 1;
    }


    while (temp->id != st->id)
    {
        prev = temp;
        temp = temp->next;
    }
    prev->next = temp->next;
    free(temp);
    l->size--;

    return 1;
}

我基本上是在尝试插入->删除->插入同一个节点

Answer 1

我刚刚更改了 list_push_back 函数，它现在可以工作了 XD。

//enters the new student in the end of the list
list list_push_back(list l, char *name, int id)
{
    student new_student = malloc(sizeof(struct studentR));
    if (new_student == NULL)
    {
        printf("Error allocating memory\n");
        abort();
    }


    strcpy(new_student->name, name);
    new_student->id = id;
    new_student->next = NULL;

    student tmp = l->head;
    if (list_isempty(l))
    {
        l->head = new_student;
    }
    else
    {
        while (tmp->next!=NULL)
        {
            tmp = tmp->next;
        }
        tmp->next = new_student;
    }
    l->tail = new_student;
    l->size++;

    return l;
}