【解决】 

  1 //**************************************************************************************************************
  2 //作者：
  3 //日期：2018/3/19
  4 //学号：
  5 //题号：5-5
  6 //题目：编写一个程序，实现以下功能：
  7 
  8 //      1)输入一系列的学生数据（包括学生的学号、姓名和成绩等基本信息），将学生信息写入二进制文件student.dat中。
  9 
 10 //      2)从student.dat文件中读出这些数据并显示出来。
 11 
 12 //      3)在student.dat文件中按姓名进行查询，如输入“李”，则将所有姓“李”的学生的   数据显示出来。
 13 
 14 //      4)可对指定学生的数据进行修改。
 15 
 16 //      5)可以删除指定的学生数据。
 17 
 18 //**************************************************************************************************************
 19 
 20 
 21 
 22 #include<iostream>
 23 #include<fstream>
 24 #include<stdlib.h>
 25 #include<cstring>
 26 using namespace std;
 27 struct Std
 28 {
 29     char name[20];
 30     char id[20];
 31     char score[5];
 32 };
 33 void getinfo(char filename[]);
 34 void showinfo(char filename[]);
 35 void searchinfo(char filename[]);
 36 void editinfo(char filename[]);
 37 void deleteinfo(char filename[]);
 38 
 39 int main()
 40 {
 41     fstream student;
 42     char choice;
 43     char filename[20];
 44     cout << "Please type in the filename:";
 45     cin.getline(filename,20);
 46     cout << endl;
 47     while(true)
 48     {
 49         cout << "Please type down the manipulation code:\nA.Input information\tB.Show information\tC.Search\tD.Edit\tE.Delete\tF.Exit\n";
 50         cout << endl;
 51         cin >> choice;
 52         switch(choice)
 53         {
 54             case'A':
 55             case'a':getinfo(filename);break;
 56             case'B':
 57             case'b':showinfo(filename);break;
 58             case'C':
 59             case'c':searchinfo(filename);break;
 60             case'D':
 61             case'd':editinfo(filename);break;
 62             case'E':
 63             case'e':deleteinfo(filename);break;
 64             case'F':
 65             case'f':exit(0);
 66         }
 67         cout << endl;
 68     }
 69     return 0;
 70 }
 71 
 72 void getinfo(char filename[])
 73 {
 74     fstream student;
 75     student.open(filename,ios::out|ios::binary);
 76     if(!student)
 77     {
 78         cout << "Error!";
 79         exit(0);
 80     }
 81     int count;
 82     cout << "How many student's information would you like to input?";
 83     cin >> count;
 84     Std *Student;
 85     Student = new struct Std[count];
 86     for(int i=0;i<count;i++)
 87     {
 88         cout << "Please input student "<<i+1<<" 's name:";
 89         cin.get();
 90         cin.getline(Student[i].name,20);
 91         cout << "Please input student "<<i+1<<" 's id:";
 92         cin.getline(Student[i].id,20);
 93         cout << "Please input student "<<i+1<<" 's score:";
 94         cin >> Student[i].score;
 95         student.write((char*)&Student[i],sizeof(Student[i]));
 96     }
 97     cout << "Done.";
 98     delete[]Student;
 99     student.close();
100 }
101 
102 void showinfo(char filename[])
103 {
104     fstream student;
105     student.open(filename,ios::in|ios::binary);
106     if(!student)
107     {
108         cout << "Error!";
109         exit(0);
110     }
111     Std Student;
112     student.read((char*)&Student,sizeof(Student));
113     while(!student.eof())
114     {
115         cout << "name:";
116         cout << Student.name <<endl;
117         cout << "id:";
118         cout << Student.id <<endl;
119         cout << "score:";
120         cout << Student.score <<endl;
121         student.read((char*)&Student,sizeof(Student));
122     }
123     cout << "Above are all the information."<<endl;
124     student.close();
125 }
126 
127 void searchinfo(char filename[])
128 {
129     fstream student;
130     Std Student;
131     student.open(filename,ios::in|ios::binary);
132     if(!student)
133     {
134         cout << "Error!";
135         exit(0);
136     }
137     char Name,ch;
138     cout << "Please input the first name:";
139     cin >> Name;
140     while(!student.eof())                   //最后一个数据块显示两次？？？
141     {
142         student.read((char*)&Student,sizeof(Student));
143         ch = Student.name[0];
144         if(ch == Name)
145         {
146             cout << "name:";
147             cout << Student.name <<endl;
148             cout << "id:";
149             cout << Student.id <<endl;
150             cout << "score:";
151             cout << Student.score <<endl;
152         }
153         cout << endl;
154     }
155     cout << "Above are all the information that you are looking for."<<endl;
156     cin.ignore();
157     student.close();
158 }
159 
160 void editinfo(char filename[])
161 {
162     fstream student;
163     Std Student;
164     student.open(filename,ios::in|ios::out|ios::binary);
165     if(!student)
166     {
167         cout << "Error!";
168         exit(0);
169     }
170     char editid[20],ID[20];
171     cout << "Please input the id of the student whose information needs to be edited:";
172     cin >> editid;
173     student.seekp(0L,ios::beg);
174     long current_position = 0;
175     while(!student.eof())
176     {
177         student.read((char*)&Student,sizeof(Student));                  //特别特别特别重要的三行！！！所以说又读又写是非常危险的！！！
178         current_position += student.tellg();
179         student.seekg(-sizeof(Student)+current_position,ios::beg);
180         /*long position1 = student.tellp();
181             cout << position1<<endl;
182         long position2 = student.tellg();
183             cout << position2<<endl;*/
184         strcpy(ID,Student.id);
185         if(strcmp(editid,ID)==0)
186         {
187             cout << "The information of the student:"<<endl;
188             cout << "name:"<<Student.name<<endl;
189             cout << "id:"<<Student.id<<endl;
190             cout << "score:"<<Student.score<<endl;
191             cout << "Now please input the new information:"<<endl;
192             cout << "name:";
193             cin >> Student.name;
194             cout << "id:";
195             cin >> Student.id;
196             cout << "score:";
197             cin >> Student.score;
198             /*long position1 = student.tellp();
199             cout << position1<<endl;*/
200             student.write((char*)&Student,sizeof(Student));
201             /*long position2 = student.tellp();
202             cout << position2<<endl;*/
203             break;
204         }
205     }
206     cout << endl;
207     cout << "Done.";
208     student.close();
209 }
210 
211 void deleteinfo(char filename[])
212 {
213     fstream student;
214     Std Student;
215     student.open(filename,ios::in|ios::binary);
216     if(!student)
217     {
218         cout << "Error!";
219         exit(0);
220     }
221     char deleid[20],ID[20];
222     cout << "Please input the id of the student whose information needs to be erased:";
223     cin >> deleid;
224     long current_position = 0;
225     while(!student.eof())
226     {
227         student.read((char*)&Student,sizeof(Student));
228         strcpy(ID,Student.id);
229         current_position = student.tellg();
230         student.seekg(-sizeof(Student)+current_position,ios::beg);
231         if(strcmp(deleid,ID)==0)
232         {
233             cout << "The information of the student:"<<endl;
234             cout << "name:"<<Student.name<<endl;
235             cout << "id:"<<Student.id<<endl;
236             cout << "score:"<<Student.score<<endl;
237             cout << "type 'd' to delete this student's information:";
238             char code;
239             cin >> code;
240             if(code == 'd')
241             {
242                 while(!student.eof())
243                 {
244                     current_position = student.tellg();
245                     student.seekg(-sizeof(Student)+current_position,ios::beg);
246             }
247             }
248 
249             student.write((char*)&Student,sizeof(Student));
250             break;
251         }
252     }
253     cout << "Done.";
254     student.close();
255 }

还是有点小问题，比如当检索的数据块为最后时会读取两次？？删除也有问题。

posted @ 2018-03-26 20:38  兔至  阅读(221)  评论(0)  编辑  收藏  举报