我的程序不能很好地完成搜索功能。为什么？
我制作了一个学生数据库程序作为我在学校的最新项目。一切正常，您可以使用ID，姓名，姓氏和标记创建记录。
这里的主要问题是; 我的代码的“名称搜索”功能。
每当我搜索带有ID的人时，它都能完美无缺，但如果我尝试用名字来做，那就会有一些问题。
如果您尝试搜索第一名学生，它会找到但绝不会搜索其他人。只会向第一名学生展示您输入的内容，如果您搜索相同长度的学生姓名，则可能会发现错误的学生。
示例1：
如你所见，我输入了Yov，但它发现了哇。
示例2：
正如您所看到的，我输入了Test作为第一个输入并且真正的学生出现了。每当我输入Stack作为以下输入时，主要问题就开始了。我期望Stack Overflow出现，但再次测试学生显示为输出。
这是我在程序中遇到的“唯一”问题。我的错误在哪里？
这是我的完整代码;
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
struct
{
long long int id;
char firstname[20];
char lastname[20];
int mark;
}student;
int main()
{
long long int idnumber;
int flag,choice,shift,found,continu,length;
char studentname[20];
FILE *fp;
printf("\n\tC PROGRAM OF STUDENT DATABASE SYSTEM");
Label1:
printf("\n1 -> Store a new record in database\n");
printf("2 -> Search a student record by Student First Name\n");
printf("3 -> Search a student record by ID\n");
printf("4 -> Quit Student Database");
printf("\n\n");
printf("Enter your choice : ");
scanf("%d",&choice);
switch(choice)
{
case 1:
Label2:
printf("\nEnter Student Details:\n\nID number: ");
scanf("%lld",&student.id);
printf("\nName:");
scanf("%s",student.firstname);
printf("\nSurname:");
scanf("%s",student.lastname);
printf("\nMark(0 - 100 integer) : ");
scanf("%d",&student.mark);
fp=fopen("studentfile.txt","a+");
fprintf(fp,"\n%lld\t%s\t%s\t%d\t",student.id,student.firstname,student.lastname,student.mark);
fclose(fp);
printf("A student record has been added successfully...\n");
printf("\n\n1 -> Wish to add another record to database");
printf("\n2 -> Wish to move to Main Menu");
printf("\n3 -> Exit from Program\n");
scanf("%d",&shift);
if(shift==1)
goto Label2;
if(shift==2)
goto Label1;
if(shift==3)
break;
if(shift!=1&&2&&3){
printf("Exiting.........");
break;
}
case 2:
Label4:
printf("\nEnter student first name: ");
scanf("%s",&studentname);
printf("Searching record with studentname=%s.\n",studentname);
found=0;
if((fp=fopen("studentfile.txt","r"))==NULL)
{
printf(" ! The File is Empty...\n\n");
}
else
{
while(!feof(fp)&& found==0)
{
fscanf(fp,"\n%lld\t%s\t%s\t%d\t",&student.id,student.firstname,student.lastname,&student.mark);
length = strlen(student.firstname);
if(student.firstname[length]==studentname[length])
found=1;
}
}
if(found)
{
printf("\nThe record is found.\n");
printf("\nID: %lld\nName: %s\nSurname: %s\nMark: %d \n",student.id,student.firstname,student.lastname,student.mark);
}
else
{
printf("Not found...\n");
getch();
}
Label5:
printf("\n\n1 -> Wish to search another record");
printf("\n2 -> Wish to move to Main Menu");
printf("\n3 -> Exit from Program\n");
scanf("%d",&shift);
if(shift==1)
goto Label4;
if(shift==2)
goto Label1;
if(shift==3)
break;
if(shift!=1&&2&&3){
printf("\nEnter a valid choice");
goto Label5;
}
case 3:
Label6:
printf("\nEnter the ID: ");
scanf("%lld",&idnumber);
printf("Searching record with ID=%lld.\n",idnumber);
found=0;
if((fp=fopen("studentfile.txt","r"))==NULL)
{
printf(" ! The File is Empty...\n\n");
}
else
{
while(!feof(fp)&& found==0)
{
fscanf(fp,"\n%lld\t%s\t%s\t%d\t",&student.id,student.firstname,student.lastname,&student.mark);
if(student.id==idnumber)
found=1;
}
}
if(found)
{
printf("\nThe record is found.");
printf("\nID no: %lld\nName: %s\nSurname: %s\nMark: %d \n",student.id,student.firstname,student.lastname,student.mark);
}
else
{
printf("Not found...\n");
getch();
}
Label7:
printf("\n\n1 -> Wish to search more..");
printf("\n2 -> Wish to move to Main Menu");
printf("\n3 -> Exit from Program\n");
scanf("%d",&shift);
if(shift==1)
goto Label6;
if(shift==2)
goto Label1;
if(shift==3)
break;
if(shift!=1&&2&&3){
printf("\nEnter a valid choice");
goto Label7;
}
case 4: break;
default :
printf(" Bad choice...Enter the choice again...\n");
goto Label1;
}
getch();
return 0;
}
1 个答案:
答案 0 :(得分：0)
这可以回答您的问题，但请修正if内容
if(student.firstname[length]==studentname[length])
必须是
if(strcmp(student.firstname[length], studentname[length]) == 0)
也
scanf("%s", &studentname);
错误应该是
scanf("%s", studentname);
它只是偶然起作用。
在这里，您可以将其视为礼物
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
struct
{
long long int id;
char firstname[20];
char lastname[20];
int mark;
} student;
void
storeRecord()
{
FILE *fp;
printf("\nEnter Student Details:\n\nID number: ");
scanf("%lld",&student.id);
printf("\nName:");
scanf("%19s",student.firstname);
printf("\nSurname:");
scanf("%19s",student.lastname);
printf("\nMark(0 - 100 integer) : ");
scanf("%d",&student.mark);
fp = fopen("studentfile.txt","a+"); /* check if the file was opened */
if (fp == NULL)
return;
fprintf(fp, "\n%lld\t%s\t%s\t%d\t",
student.id,
student.firstname,
student.lastname,
student.mark);
fclose(fp);
printf("A student record has been added successfully...\n");
getchar();
}
void
printStudent()
{
printf("\nThe record is found.\n");
printf("\nID: %lld\nName: %s\nSurname: %s\nMark: %d \n",
student.id,
student.firstname,
student.lastname,
student.mark
);
}
void
searchStudentByName()
{
char studentname[20];
FILE *fp;
int found;
int matches;
printf("\nEnter student first name: ");
scanf("%19s", studentname);
printf("Searching record with studentname=%s.\n", studentname);
found = 0;
fp = fopen("studentfile.txt", "r");
if (fp == NULL)
{
printf("IO error\n");
return;
}
matches = fscanf(fp,"\n%lld\t%s\t%s\t%d\t",
&student.id,
student.firstname,
student.lastname,
&student.mark);
do
{
matches = fscanf(fp,"\n%lld\t%s\t%s\t%d\t",
&student.id,
student.firstname,
student.lastname,
&student.mark);
if (matches == 4)
found = (strcmp(student.firstname, studentname));
} while ((matches == 4) && (found == 0));
if (found != 0)
printStudent();
else
printf("Not found...\n");
getchar();
}
void
searchStudentById()
{
int id;
int found;
int matches;
FILE *fp;
printf("\nEnter student first name: ");
scanf("%d", &id);
printf("Searching record with id=%d.\n", id);
found = 0;
fp = fopen("studentfile.txt", "r");
if (fp == NULL)
{
printf("IO error\n");
return;
}
do
{
matches = fscanf(fp,"\n%lld\t%s\t%s\t%d\t",
&student.id,
student.firstname,
student.lastname,
&student.mark);
if (matches == 4)
found = (student.id == id);
} while ((matches == 4) && (found == 0));
if (found != 0)
printStudent();
else
printf("Not found...\n");
getchar();
}
int main()
{
int choice;
choice = 0;
while (choice != 4)
{
printf("\n\tC PROGRAM OF STUDENT DATABASE SYSTEM");
printf("\n1 -> Store a new record in database\n");
printf("2 -> Search a student record by Student First Name\n");
printf("3 -> Search a student record by ID\n");
printf("4 -> Quit Student Database");
printf("\n\n");
printf("Enter your choice : ");
scanf("%d",&choice);
switch(choice)
{
case 1:
storeRecord();
break;
case 2:
searchStudentByName();
break;
case 3:
searchStudentById();
break;
}
}
return 0;
}
这是可读的，并且在DRY原则方面还有一个改进。你显然忽略了这一点。
您不需要将学生宣布为全球学生。
此代码优于前一个代码
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
struct Student
{
long long int id;
char firstname[20];
char lastname[20];
int mark;
} student;
void
storeRecord()
{
FILE *fp;
printf("\nEnter Student Details:\n\nID number: ");
scanf("%lld",&student.id);
printf("\nName:");
scanf("%19s",student.firstname);
printf("\nSurname:");
scanf("%19s",student.lastname);
printf("\nMark(0 - 100 integer) : ");
scanf("%d",&student.mark);
fp = fopen("studentfile.txt","a+"); /* check if the file was opened */
if (fp == NULL)
return;
fprintf(fp, "\n%lld\t%s\t%s\t%d\t",
student.id,
student.firstname,
student.lastname,
student.mark);
fclose(fp);
printf("A student record has been added successfully...\n");
getchar();
}
int
compareStudentsById(struct Student lhs, struct Student rhs)
{
return (lhs.id == rhs.id);
}
int
compareStudentsByName(struct Student lhs, struct Student rhs)
{
return (strcmp(lhs.firstname, rhs.firstname) == 0);
}
void
printStudent()
{
printf("\nThe record is found.\n");
printf("\nID: %lld\nName: %s\nSurname: %s\nMark: %d \n",
student.id,
student.firstname,
student.lastname,
student.mark
);
}
void
searchStudent(int(*compare)(struct Student,struct Student), const char *const name, int id)
{
FILE *fp;
int found;
int matches;
if (name != NULL)
printf("Searching record with Name = %s.\n", name);
if (id != -1)
printf("Searching record with ID = %d.\n", id);
found = 0;
fp = fopen("studentfile.txt", "r");
if (fp == NULL)
{
printf("IO error\n");
return;
}
matches = fscanf(fp,"\n%lld\t%s\t%s\t%d\t",
&student.id,
student.firstname,
student.lastname,
&student.mark);
do
{
struct Student other;
if (name != NULL)
strcpy(other.firstname, name);
other.id = id;
matches = fscanf(fp,"\n%lld\t%s\t%s\t%d\t",
&student.id,
student.firstname,
student.lastname,
&student.mark);
if (matches == 4)
found = (compare(student, other) != 0);
} while ((matches == 4) && (found == 0));
if (found != 0)
printStudent();
else
printf("Not found...\n");
getchar();
}
void
searchStudentByName()
{
char studentname[20];
printf("\nEnter student first name: ");
scanf("%19s", studentname);
searchStudent(compareStudentsByName, studentname, -1);
}
void
searchStudentById()
{
int id;
printf("\nEnter student first name: ");
scanf("%d", &id);
searchStudent(compareStudentsByName, NULL, id);
}
int main()
{
int choice;
choice = 0;
while (choice != 4)
{
printf("\n\tC PROGRAM OF STUDENT DATABASE SYSTEM");
printf("\n1 -> Store a new record in database\n");
printf("2 -> Search a student record by Student First Name\n");
printf("3 -> Search a student record by ID\n");
printf("4 -> Quit Student Database");
printf("\n\n");
printf("Enter your choice : ");
scanf("%d",&choice);
switch(choice)
{
case 1:
storeRecord();
break;
case 2:
searchStudentByName();
break;
case 3:
searchStudentById();
break;
}
}
return 0;
}
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