函数fun的功能是将存放学生数据的结构体数组按照姓名的字典序（从小到大）排序，在fun函数内采用的选择排序法，选择排序法中的升序排序，首先从数组中挑选一个元素，把它和第一元素交换，接着从剩下的n-1个元素中再挑出一个最小的元素，把它和第二个元素交换，不断重复以上过程，直到比较完最后两个元素。

-Function fun function is to store the data structure an array of students by name, the dictionary order (from small to large) order, within the function in the fun using the Selection Sort, Selection Sort in ascending order, first select from an array elements, the first element of it and exchange, and then from the remaining n-1 elements in another single out one of the least element of it and the second element of exchange, constantly repeat the process until more complete the last two elements .