求教一个排序问题

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>
#include<fcntl.h>
#include"student_grade.h"

//sort linked list by final grade score in descending order
student *sort_finalGrade(student *head){
student *left = NULL;
student *miniNode = NULL;
student *end = head;
student *tmp = NULL;
int sorted;

do{
end = head;
while(end!=miniNode){
left = end->next;
if(left != NULL){
if(end->stu_final_aver < left->stu_final_aver){
tmp = left->next;
left->next = end;
end->next = tmp;
}
}// end outer if
end = end->next;
}// end while
miniNode = end;
head = left;
}while(head != miniNode);
return head;
}

//print the sorted list to the output file
void write_OutPut(student *head,FILE *fout){
//head = sort_finalGrade(head);
student *p=head;
char tmp[1024]={0};
while (p!=NULL){
sprintf(tmp,"%s %d\nWeighted percentile score:%3.0lf\nFinal grade:%0.1lf\n\n",
p->student_name,p->student_id,
p->stu_final_aver,p->student_final
);
fwrite(tmp,1,strlen(tmp),fout);
p=p->next;
}// end while
}


一个冒泡排序的类, 感觉有问题, 请高手指教