C程序设计 （第四版） 谭浩强 习题10.6

习题10.6 将第5题"stud"文件中的学生数据，按平均分进行排序处理，将已排序的学生数据存入一个新文件"stu_sort"中。

IDE工具：VS2010

Note: 使用不同的IDE工具可能有部分差异。

代码块

方法：使用指针，函数的模块化设计，动态分配内存

说明：这里准备读取的文件名stud.dat，文件已经存在于该项目目录下，准备写入的文件stu_sort.dat通过程序建立。

#include <stdio.h>
#include <stdlib.h>#define N 5typedef struct{int num;char name[20];float score[3];float aver;
}Student;void initialStu(Student **stu, int n, char **name){*stu = (Student*)malloc(n * sizeof(Student));*name = (char*)malloc(80 * sizeof(char));
}//以下注释段的代码为第5题中的输入学生信息
/*
void inputStu(Student *stu, int n){printf("Enter %d student info:\n\n", n);for(int i = 0; i < n; i++){printf("Enter No.%d student number(100 ~ 999): ", i + 1);scanf("%d", &stu[i].num);while(stu[i].num < 100 || stu[i].num > 999){printf("Number Error! Retry!\nEnter No.%d student number(100 ~ 999): ", i + 1);scanf("%d", &stu[i].num);}fflush(stdin);printf("Enter No.%d student name: ", i + 1);gets(stu[i].name);float sum = 0.0;for(int j = 0; j < 3; j++){printf("Enter No.%d student No.%d course score(0 ~ 100): ", i + 1, j + 1);scanf("%f", &stu[i].score[j]);while(stu[i].score[j] < 0 || stu[i].score[j] > 100){printf("Score Error! Retry!\nEnter No.%d student No.%d course score(0 ~ 100): ", i + 1, j + 1);scanf("%f", &stu[i].score[j]);}sum += stu[i].score[j];}stu[i].aver = sum / 3;printf("\n");}printf("\n");
}
*/void sortByAverStu(Student *stu, int n){Student temp;for(int i = 0; i < n; i++){for(int j = i + 1; j < n; j++){if(stu[i].aver < stu[j].aver){temp = stu[i];stu[i] = stu[j];stu[j] = temp;}}}
}void inputFileName(FILE **file, char *name){printf("Enter File Name: ");scanf("%s", name);*file = fopen(name, "rb");if(*file == NULL){perror("Cannot open this file");system("pause");exit(0);}
}void readFileAndSort(FILE **file, char *name, Student *stu, int n){for(int i = 0; i < n; i++){fread(&stu[i], sizeof(Student), 1, *file);}sortByAverStu(stu, n);
}void inputFile(FILE **file, char *name, Student *stu, int n){printf("Enter New File Name: ");scanf("%s", name);*file = fopen(name, "wb");if(*file == NULL){perror("File Error");system("pause");exit(0);}for(int i = 0; i < n; i++){if(fwrite(&stu[i], sizeof(Student), 1, *file) != 1){perror("File write error");system("pause");exit(0);}}fclose(*file);
}void outputFile(FILE **file, char *name, Student *stu, int n){*file = fopen(name, "rb");if(*file == NULL){perror("Cannot open this file");system("pause");exit(0);}printf("Read File Info:\n");for(int i = 0; i < n; i++){fread(&stu[i], sizeof(Student), 1, *file);printf("Number: %-3d  Name: %-10s  Score: ", stu[i].num, stu[i].name);for(int j = 0; j < 3; j++){printf("%-3.2f  ", stu[i].score[j]);}printf("Average: %-3.2f\n", stu[i].aver);}printf("\n");fclose(*file);
}void freeStu(Student **stu, char **name){free(*stu);free(*name);
}int main(){FILE *file1 = NULL;FILE *file2 = NULL;Student *stu = NULL;char *name = NULL;initialStu(&stu, N, &name);inputFileName(&file1, name);outputFile(&file1, name, stu, N);readFileAndSort(&file1, name, stu, N);inputFile(&file2, name, stu, N);outputFile(&file2, name, stu, N);freeStu(&stu, &name);system("pause");return 0;
}

运行结果如下：