C語言程序設計 練習題參考答案 第八章 文件（2）

/* 8.８從文件ex88_1.txt中取出成績，排序后，按降序存放EX88_2.TXT中 */
#include "stdio.h"
#define N 10
struct student
{
? int num;
? char name[20];
? int score[3];? /*不能使用float*/
? float average;
};

void sort(struct student stu[]);
void print(FILE *fp, struct student stu[]);
void printtopfive(FILE *fp, struct student stu[]);

void main()
{
?? struct student s[N];
?? int i;
?? FILE *fp1,*fp2;
??? char ch;
??? if((fp1=fopen("c:\\ex88_1.txt","r"))==NULL)
????? {
?????? printf("不能打開文件c:\\ex88_1.txt");
?????? exit(1);
????? }
??? if((fp2=fopen("c:\\ex88_2.txt","w"))==NULL)
????? {
?????? printf("不能打開文件c:\\ex88_2.txt");
?????? exit(1);
????? }

?? for(i=0;i<N;i++)
?? {
????? fscanf(fp1,"%d%s%d%d%d",&s[i].num,s[i].name,&s[i].score[0],
??????????????????????? &s[i].score[1],&s[i].score[2]);
????? s[i].average=(s[i].score[0]+s[i].score[1]+s[i].score[2])/3.0;
?? }
?? fprintf(fp2,"原始成績報表\n");
?? print(fp2,s);
?? sort(s);
?? fprintf(fp2,"排序之后的成績報表\n");
?? print(fp2,s);
?? fprintf(fp2,"前五名成績報表\n");
?? printtopfive(fp2,s);
}

void sort(struct student stu[])
{
? int i,k,j;
? struct student t;
? for(i=0;i<N-1;i++)
? {
??? k=i;
??? for(j=i+1;j<N;j++)
??? {
????? if(stu[k].average<stu[j].average)
???????? k=j;
????? if(k!=i)
????? {
?????? t=stu[i];
?????? stu[i]=stu[k];
?????? stu[k]=t;
????? }
??? }

?? }
}

void print(FILE *fp, struct student stu[])
{
?int i;
?fprintf(fp,"StudentID StudentName?? Score1? Score2? Score3? Average\n");
?for(i=0;i<N;i++)
?? fprintf(fp,"%-10d%-12s%8d%8d%8d%8.1f\n",stu[i].num,stu[i].name,
?? stu[i].score[0],stu[i].score[1],stu[i].score[2],stu[i].average);
}

void printtopfive(FILE *fp, struct student stu[])
{
?int i;
?fprintf(fp,"StudentName?? Average\n");
?for(i=0;i<5;i++)
?? fprintf(fp,"%-12s%8.1f\n",stu[i].name,stu[i].average);
}

/*ex88_1.txt中取出成績?

20001??? 姓名（1）??? 70??? 80??? 90
20002??? 姓名（2）??? 71??? 81??? 91
20003??? 姓名（3）??? 72??? 82??? 92
20004??? 姓名（4）??? 73??? 83??? 93
20005??? 姓名（5）??? 74??? 84??? 94
20006??? 姓名（6）??? 75??? 85??? 95
20007??? 姓名（7）??? 76??? 86??? 96
20008??? 姓名（8）??? 77??? 87??? 97
20009??? 姓名（9）??? 78??? 88??? 98
20010??? 姓名（10）??? 79??? 89??? 99
*/

/*排序后，按降序存放EX88_2.TXT中

原始成績報表
StudentID StudentName?? Score1? Score2? Score3? Average
20001???? 姓名（1）???????? 70????? 80????? 90??? 80.0
20002???? 姓名（2）???????? 71????? 81????? 91??? 81.0
20003???? 姓名（3）???????? 72????? 82????? 92??? 82.0
20004???? 姓名（4）???????? 73????? 83????? 93??? 83.0
20005???? 姓名（5）???????? 74????? 84????? 94??? 84.0
20006???? 姓名（6）???????? 75????? 85????? 95??? 85.0
20007???? 姓名（7）???????? 76????? 86????? 96??? 86.0
20008???? 姓名（8）???????? 77????? 87????? 97??? 87.0
20009???? 姓名（9）???????? 78????? 88????? 98??? 88.0
20010???? 姓名（10）??????? 79????? 89????? 99??? 89.0
排序之后的成績報表
StudentID StudentName?? Score1? Score2? Score3? Average
20010???? 姓名（10）??????? 79????? 89????? 99??? 89.0
20009???? 姓名（9）???????? 78????? 88????? 98??? 88.0
20008???? 姓名（8）???????? 77????? 87????? 97??? 87.0
20007???? 姓名（7）???????? 76????? 86????? 96??? 86.0
20006???? 姓名（6）???????? 75????? 85????? 95??? 85.0
20005???? 姓名（5）???????? 74????? 84????? 94??? 84.0

*/