Question

我正在编写一个程序，将天数打印到供学生使用的文件中。低端是他们将从一个列表中进行选择，并击中了我下面的switch statemtnt，在其中调用了我的打印语句。在print语句中，它将具有数据结构的排序功能。但是我对如何编写函数进行排序感到有些困惑。我想按MWF和TR排序

在这里出现查询语句，在查询语句下方是天数排序。

#include<stdio.h>
#include<string.h>
    #include "student.h"
    class_t classes[20];


    void queryUser(class_t classes[], int n){
    // This will prompt the user what they would like to do within the program
    // the idea here is to decide how each function needs to run
    char year;
    char user = 'a';
    char *time = " ";
    char *day = " ";
    char nl;
    // FILE* iptr = fopen("/public/csci112sp19/pgm1/classes.txt", "r");
    FILE* fptr = fopen("out.txt", "w");
    while(user != 'Q'){
        printf("What would you like to do?\n");
        printf("Print all classes: A\n");
        printf("Print all classes by day: B\n");
        printf("Print Classes by time: C\n");
        printf("Print all classes for student year: D \n");
        printf("Quit : Q\n");
        scanf("%c%c", &user, &nl);


        // there will be an switch case statement in this function
        // similar to if statements, if a case is called
        // the function will dictate what will print the information
        // stored in the selected array
        // put lower case in also
        printf("user is %c and n is %d\n", user, n);
        switch(user){
            case 'A':
                printAllClasses(classes, n,fptr);
                break;

            case 'B':
                printf("What days would you like to sort by MWF or TR?");
                scanf("%s", day);
                scanf("%c", &nl);
                printClassDay(classes, day , n, fptr);
                break;
            case 'C':
                printf("what time and what day");
                scanf("%s %s", time, day);
                scanf("%c", &nl);
                printClassTime(classes, day, time, n, fptr);
                //search array for day and time matching
                break;
            case 'D':
                printf("Please enter what year in school, Fresh: 1, Soph: 2, JR: 3, SR, 4\n");

                scanf("%c", &year);
                scanf("%c", &nl);
                yearMethod(classes, year, n, fptr);
                break;
            case 'Q':
                break;
            default:
                printf("Please use capital letters\n");
        }
    }
}
$


void sortbyclassdays(class_t classes[], int n, FILE* fptr){

    int i, j, doswap = 0;

    class_t temp;

    for (i = 0; i < n; ++i) {
        for (j = i; j < n; ++j) {
            doswap = strcmp(classes[i].classDays, classes[j].classDays);
        }

        if (doswap > 0) {
            temp = classes[i];
            classes[i]= classes[j];
            classes[j] = temp;
        }
    }

    return;
}


void printClassDay(class_t classDays[], char* day, int n, FILE* fptr){
    //this method will print classes by days selected by user
    sortbyclassdays(classes, n, fptr);
    for(int i = 0; i < n; ++i){
        if(strcmp(day,"MWF")){
            printOneClass(classes[i], fptr);
        }
        else if(strcmp(day, "TR")){
            printOneClass(classes[i], fptr);
        }
    }
    return;

Answer 1

关于：

printf("What would you like to do?\n");
printf("Print all classes: A\n");
printf("Print all classes by day: B\n");
printf("Print Classes by time: C\n");
printf("Print all classes for student year: D \n");
printf("Quit : Q\n");

函数printf()是CPU周期的昂贵消耗者。

“菜单”将难以阅读和理解。

建议：

printf("%s", 
       "\nWhat would you like to do?\n"
       "A: Print all classes:\n"
       "B: Print all classes by day:\n"
       "C: Print Classes by time:\n"
       "D: Print all classes for student year:\n"
       "Q: Quit\n");

甚至更好：

puts(  "\nWhat would you like to do?\n"
       "A: Print all classes:\n"
       "B: Print all classes by day:\n"
       "C: Print Classes by time:\n"
       "D: Print all classes for student year:\n"
       "Q: Quit\n");

OT：关于：

scanf("%c%c", &user, &nl);

在调用任何scanf（）系列函数时，请始终检查返回的值以确保操作成功。注意：返回的值为EOF或成功的输入格式说明符转换的次数。在当前情况下，建议：

if( scanf("%c%c", &user, &nl) != 2) 
{ 
    // handle error 
}

关于这种陈述：

scanf("%c", &nl);

强烈建议使用：

int nl; 
while( (nl = getchar() ) != '\n' && nl != EOF );

关于：

for (j = i; j < n; ++j) 
{ 
    doswap = strcmp(classes[i].classDays, classes[j].classDays); 
}

这将遍历所有“ classDays”，然后退出循环，因此下一个代码块：，以：开头：

if (doswap > 0)

将仅查看数组中的最后一个条目。因此，其他所有数据都不会排序。

您的编译器“可以”让您摆脱困境：

 default:
     printf("Please use capital letters\n");

但是，在致电printf()之后应该是：

     break;

关于：

switch(user)

如果用户输入小写字母，这将不起作用。

建议：

switch( toupper(user) )

关于：

char user = 'a';

名称user并不代表其内容。

建议更有意义的内容，例如：

selection

关于：

void sortbyclassdays(class_t classes[], int n, FILE* fptr){

未使用函数参数FILE *fptr。建议在代码的其余部分中删除该功能参数及其所有引用

关于：

if(strcmp(day,"MWF")){
        printOneClass(classes[i], fptr);
    }

为什么跳过在“天”字段中具有“ MWF”的记录？

关于：

else if(strcmp(day, "TR")){
        printOneClass(classes[i], fptr);
    }

为什么跳过day字段中具有“ TR”的记录？

发布的代码缺少main()函数，并且缺少该函数的最后}：printClassDay()

强烈建议您使用实际有效的排序算法替换函数sortbyclassdays()的主体。建议：bubble sort

发布的代码中缺少功能printOneClass()。

OT：声明为返回void的函数具有'return`语句。不需要那句话

关于如下语句：

temp = classes[i];
classes[i]= classes[j];
classes[j] = temp;

这些语句实际上不会移动整个struct class_t

建议：

memcpy( &temp, &classes[i], sizeof( class_t ) );
memcpy( &classes[i], &classes[j], sizeof( class_t ) );
memcpy( &classes[j], &temp, sizeof( class_t ) );

需要帮助按天打印排序的文件

1 个答案: