1.　　设计一个学生类student，包括学生学号、姓名、成绩；设计一个友元函数，比较某两个学生成绩的高低；读入一个文本文件（格式如示例studengt.txt，每行的学号、姓名、成绩之间用四个空格隔开）中所有学生的学号、姓名、成绩，输出最高成绩和最低成绩的学生信息（学号、姓名、成绩）。-design a student class student, including student id, name, student achievement, Design a friend yuan, a function of two students, Read a text file formats such as examples studengt. (the row, TXT student id, name, with four separate space between the results of all students) student id, name, scores the highest and lowest grades, the output of the students　grades (student id, name, grades).