建立一个动态链表，将学生数据（学号，成绩）存入链表结构中，实现链表的访问（求学生成绩的平均分，找到最高分，最低分，将其数据输出）。删除指定学号的学生数据，对学生数据进行排序，分别在链表头部，中间，末尾插入学生数据。-To establish a dynamic linked list, students and student id data (deposited in the list, realize the list of access (the average student achievement, find the lowest points, points, data output). Remove the student, the student id student sorting, data in the chain, respectively, at the head into student data.