大哥帮解释一下
#include<stdio.h>
#include<stdlib.h>
#define XIN sizeof(struct student)
typedef struct student{
int number;
char name[4];
int score1;
int score2;
int score3;
float average;
struct student *node;
}xin;
int main(){
FILE *fp;
xin *p1,*p2,*p3,*head,m;
int i=0;
head=NULL;
if((fp=fopen("stud","r"))==NULL){
printf("无法打开此文件");
exit(0);
}
p1=p2=(xin *)malloc(XIN);
fscanf(fp,"%d %s %d %d %d %f\n",&p1->number,p1->name,&p1->score1,&p1->score2,&p1->score3,&p1->average);
while(!feof(fp)){
if(i==0)head=p1;
else p2->node=p1;
p2=p1;
p1=(xin*)malloc(XIN);
i++;
fscanf(fp,"%d %s %d %d %d %f\n",&p1->number,p1->name,&p1->score1,&p1->score2,&p1->score3,&p1->average);
}
p2->node=p1;
p1->node=NULL;
fclose(fp);
p2=&m;
p2->node=head;
while(i+1!=0){
for(p1=head;p1->node!=NULL;){
if(p1->average<p1->node->average){
p3=p1->node->node;
p2->node=p1->node;
p2->node->node=p1;
p1->node=p3;
if(p2==&m)head=p2->node;
p1=p2->node;
}
p2=p1; //为什么这"p2=p2->node"就段错误,这两个不是一样的吗。
p1=p1->node;
}
i--;
}
if((fp=fopen("stu_sort","w"))==NULL){
printf("无法打开此文件");
exit(0);
}
p3=head;
while(p3!=NULL){
fprintf(fp,"%d %s %d %d %d %6.2f\n",p3->number,p3->name,p3->score1,p3->score2,p3->score3,p3->average);
p3=p3->node;
}
fclose(fp);
return 0;
}