不知道错哪儿了,Vector的操作不会

[didoleo]

//片段:有个Hotel类,
class Hotel {
public:
int hotel_code;
char hotel_name[50];
char hotel_city[50];

int total_regular_rooms;
double tariff_regular_room;
int available_regular_rooms;

int total_deluxe_rooms;
double tariff_deluxe_room;
int available_deluxe_rooms;
}
//.....
//省略
//.....
vector<Hotel> Vh(1);
Hotel h;
ofstream OutputFile;
ifstream InputFile;

//....前面从cin读进了几条Hotel的记录然后准备望文件里写.(不知道Vh.size()这个有没问题,
我明明只输入了一条记录,但Vh.size()返回的却是2,总是成倍的???????
)
for(int n=0;n<Vh.size();n++){
OutputFile.write((char*)&Vh[n],sizeof(Vh[n]));
}

InputFile.read((char*)&h,sizeof(h));
while(!InputFile.eof())
{
Vh.push_back(h);
InputFile.read((char*)&h,sizeof(h));

}
InputFile.close();
InputFile.clear();

//下面我输出从文件里读出来的记录,下面的内容是对的,但是老是会在前面先打出一大堆乱码来,
//why??
for(int n=0;n<Vh.size();n++){
cout<<Vh[n].hotel_code<<endl;
cout<<Vh[n].hotel_name<<endl;
cout<<Vh[n].hotel_city<<endl;

}

谢谢各位老大.

[didoleo]

#include <iostream>
#include <string>

#include <fstream>
#include <stdlib.h>

#include <vector>
#include <algorithm>
using namespace std;

void dispMenu();
char* filename="hotel.dat";
class Hotel {
public:
int hotel_code;
char hotel_name[50];
char hotel_city[50];

int total_regular_rooms;
double tariff_regular_room;
int available_regular_rooms;

int total_deluxe_rooms;
double tariff_deluxe_room;
int available_deluxe_rooms;

void print()
{
cout<<endl<<"旅馆代码: "<<hotel_code;
cout<<endl<<"旅馆名称: "<<hotel_name;
cout<<endl<<"旅馆所在城市: "<<hotel_city;

cout<<endl<<"总共标准房间: "<<total_regular_rooms;
cout<<endl<<"标准房间价格: "<<tariff_regular_room;
cout<<endl<<"可用标准房: "<<available_regular_rooms;

cout<<endl<<"总共豪华房间: "<<total_deluxe_rooms;
cout<<endl<<"豪华房间价格: "<<tariff_deluxe_room;
cout<<endl<<"可用豪华房: "<<available_deluxe_rooms;

}



};


int getMaxCode(char *filename)
{
int maxhotelcode=0;
ifstream InputFile;

vector<Hotel> Vh(1);
Hotel h;
InputFile.open(filename,ios::in);


while(!InputFile.eof())
{
InputFile.read((char*)&h,sizeof(h));
//cout<<h.hotel_city<<" "<<h.hotel_code<<" "<<h.hotel_name<<endl;
Vh.push_back(h);
}
InputFile.close();
InputFile.clear();



for(int n=0;n<Vh.size();n++)
{
//maxhotelcode++;
//Vh[n].hotel_code=maxhotelcode;
maxhotelcode=Vh[n].hotel_code;
}
return maxhotelcode+1;

};



void addNewHotel(char *filename)
{
system("cls");
ofstream OutputFile;
ifstream InputFile;
vector<Hotel> Vh(1);
Hotel h;
int maxhotelcode=1;
int hotelcode;
InputFile.open(filename,ios::binary|ios::in);

if(!InputFile){

hotelcode=1;
}else
{
//int o=0;
InputFile.read((char*)&h,sizeof(h));

while(!InputFile.eof())
{
Vh.push_back(h);
cout<<maxhotelcode;
maxhotelcode++;
InputFile.read((char*)&h,sizeof(h));

}
InputFile.close();
InputFile.clear();


}


cout << " ADD NEW HOTEL DETAILS" << endl;
cout << "New Hotel Code is:"<<maxhotelcode<<endl;



OutputFile.open(filename,ios::binary|ios::out);


char reply='Y';



h.hotel_code=maxhotelcode;
maxhotelcode++;
cout << "Enter Hotel/Resort name:" << endl;
cin >>h.hotel_name;
cout << "Enter City name:" << endl;
cin >> h.hotel_city;
cout << "Enter the number of Regular rooms:" << endl;
cin >> h.available_regular_rooms;
cout << "Enter the tariff for Regular rooms:" << endl;
cin >> h.tariff_regular_room;
cout << "Enter the number of Deluxe rooms:" << endl;
cin >> h.available_deluxe_rooms;
cout << "Enter the tariff for Deluxe rooms:" << endl;
cin >> h.tariff_deluxe_room;

Vh.push_back(h);



for(int n=0;n<Vh.size();n++){
//cout<<Vh[n].hotel_code<<endl;
//cout<<Vh[n].hotel_name<<endl;
//cout<<Vh[n].hotel_city<<endl;
OutputFile.write((char*)&Vh[n],sizeof(Vh[n]));
}


OutputFile.close();
OutputFile.clear();
dispMenu();

}

void addNewResort()
{

}

void recBooking()
{

}

void recCancel()
{

}

void viewDetail()
{

}

void dispMenu()
{
system("cls");
int menuitem;
cout << " HOTEL BOOK SYSTEM" << endl;
cout << "1. Add new Hotel details" << endl;
cout << "2. Add new Resort details" << endl;
cout << "3. Record Booking details" << endl;
cout << "4. Record Cancellation details" << endl;
cout << "5. View details or Hetels and Resorts in a city" << endl;
cout << "6. Exit" << endl;
cout << " Enter choice:";
cin >> menuitem;
switch(menuitem){
case 1: addNewHotel(filename);
break;
case 2: addNewResort();
break;
case 3: recBooking();
break;
case 4: recCancel();
break;
case 5: viewDetail();
break;
case 6: exit(0);
break;
default: dispMenu();
break;
};

}

void main()
{


dispMenu();

}

[didoleo]

不好意思,我学c++才一个星期,这是作业题目,我写的不规范,不要笑我.

[didoleo]

to: defyer007(挑战者---在学MFC呢)

Vh.size()我的理解应该是有多少记录有应该是多少,比如文件里两条记录,那么读到Vh里面,
Vh.size()就应该是2吧,但实际上我跟踪了一写Vh.size()是4

晕倒

[zengwujun]

vector<Hotel> Vh(1);这样是定义了一个只有能容纳一个元素的数组,但这个元素是空的.
vector的好处就是他会随着记录的增加自动扩大容量.我定义vector<Hotel> Vh(100)也可以
他只表明了他的容量,就象 int intArr[100],这个intArr里面没东西的,除非我给他们都赋值

------------------------------------------------------------------------------
vector<Hotel> Vh(100)表明要给Vh分配100个元素，元素内容是空的，如果capacity不够，
vector会自动增加已满足能分配100元素的空间,这时Vh.size()=100;capacity可能为100，
也可能>100.

[antter]

vector<Hotel> Vh(1);
你的vector初始不为空，size所以比原来多1，1+1=2 一次会存入两条.
displayMenu()递归调用，在极端可能下，比如操作了上万次，会发生堆栈溢出。

[1982pc]

楼主你说的是,可是你用push_back表示在队尾+如一个元素,这样vector就会自动增加1了!你只要把声明改成vector<Hotel> Vh;就可以了!

[didoleo]

to: WuYL7812(龙哥)
1982pc()
zengwujun(月之海)

太谢谢你们了,现在对了!
下午借了本书看看,也知道了,呵呵.

[useresu]

你push_back(h);两次的原因吧

void addNewHotel(char *filename)
{
system("cls");
ofstream OutputFile;
ifstream InputFile;
vector<Hotel> Vh(1);
Hotel h;
int maxhotelcode=1;
int hotelcode;
InputFile.open(filename,ios::binary|ios::in);

if(!InputFile){

hotelcode=1;
}else
{
//int o=0;
InputFile.read((char*)&h,sizeof(h));

while(!InputFile.eof())
{
Vh.push_back(h);//第一次
cout<<maxhotelcode;
maxhotelcode++;
InputFile.read((char*)&h,sizeof(h));

}
InputFile.close();
InputFile.clear();


}


cout << " ADD NEW HOTEL DETAILS" << endl;
cout << "New Hotel Code is:"<<maxhotelcode<<endl;



OutputFile.open(filename,ios::binary|ios::out);


char reply='Y';



h.hotel_code=maxhotelcode;
maxhotelcode++;
cout << "Enter Hotel/Resort name:" << endl;
cin >>h.hotel_name;
cout << "Enter City name:" << endl;
cin >> h.hotel_city;
cout << "Enter the number of Regular rooms:" << endl;
cin >> h.available_regular_rooms;
cout << "Enter the tariff for Regular rooms:" << endl;
cin >> h.tariff_regular_room;
cout << "Enter the number of Deluxe rooms:" << endl;
cin >> h.available_deluxe_rooms;
cout << "Enter the tariff for Deluxe rooms:" << endl;
cin >> h.tariff_deluxe_room;

Vh.push_back(h);//第二次



for(int n=0;n<Vh.size();n++){
//cout<<Vh[n].hotel_code<<endl;
//cout<<Vh[n].hotel_name<<endl;
//cout<<Vh[n].hotel_city<<endl;
OutputFile.write((char*)&Vh[n],sizeof(Vh[n]));
}


OutputFile.close();
OutputFile.clear();
dispMenu();

}

[owe]

借人气问一下，在类的属性里面定义Vector怎么定义啊？
比如用上面的为例：
///////////////////////////
#include <iostream>
#include <vector>
using namespace std;

class Hotel {
private:
vector<int> v(10); // 在这里出错！！
public:
//vector<int> v(10);
int hotel_code;
Hotel()
{
hotel_code = 100;
//v[0] = 20;

}
void print()
{
vector<int> Vh(1);
Vh[0] = 12;
cout<<endl<<"旅馆代码: "<<hotel_code << " Vector " <<Vh[0];
}
};

int main()
{
Hotel h;
h.print();
system("PAUSE");
return 0;
}
//////////////////
谢谢啊

[didoleo]

to: useresu(俗人) 的确Vh.push_back(h)两次
第一次:
if(!InputFile){

hotelcode=1;
}else
{
//int o=0;
InputFile.read((char*)&h,sizeof(h));

while(!InputFile.eof())
{
Vh.push_back(h);
cout<<maxhotelcode;
maxhotelcode++;
InputFile.read((char*)&h,sizeof(h));

}
InputFile.close();
InputFile.clear();


}
目的是从文件中读出记录数,push_back一次,我认为就是读了一条记录,这个概念不知道对不对,用maxhotelcode++来累计记录总数,目的要得到一个当前可用的最大hotel的编号.文件读完了,Vh里面因该是已有的记录.

第二次push_back是在这
h.hotel_code=maxhotelcode;
maxhotelcode++;
cout << "Enter Hotel/Resort name:" << endl;
cin >>h.hotel_name;
cout << "Enter City name:" << endl;
cin >> h.hotel_city;
cout << "Enter the number of Regular rooms:" << endl;
cin >> h.available_regular_rooms;
cout << "Enter the tariff for Regular rooms:" << endl;
cin >> h.tariff_regular_room;
cout << "Enter the number of Deluxe rooms:" << endl;
cin >> h.available_deluxe_rooms;
cout << "Enter the tariff for Deluxe rooms:" << endl;
cin >> h.tariff_deluxe_room;

Vh.push_back(h);//第二次

这是从键盘输入的新的记录被push_back进来,由于我是覆盖文件的,把整个Vh重新写回文件,覆盖掉文件中老的记录(老师说一定要覆盖掉,不要追加).
现在的问题是我每次得到的hotel的编号总是2,4,6,8.....这样下去的,好象就是说文件里的记录被写进了两次,我在循环里面用的Vh.size(),我不确定这个size()到底代表什么,他为什么不能准确反映Vh数组大小呢?

谢谢

[1982pc]

Vh.size()代表当前vector的大小,虽然不太懂你说的,但你说的大小问题确实是由于你push_back两次造成的!

[didoleo]

因为有新的记录从键盘上录入,push_back两次,第一次是push_bak的文件里的老的记录,第二次是push_back的刚录入的新的记录,新老记录重新覆盖文件,是这样的流程.两次push_back的不一样的内容.

下面是我写进hotel.dat的内容:我录入了3条记录,的确没重复,但读出来的时候Vh.size()不是3,比3大?!


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[1982pc]

对不起啊.按你的代码得的结果确实是这样.
void addNewHotel(char *filename)
{
system("cls");
ofstream OutputFile;
ifstream InputFile;
vector<Hotel> Vh(1);
Hotel h;
int maxhotelcode=1;
int hotelcode;
InputFile.open(filename,ios::binary|ios::in);

if(!InputFile){

hotelcode=1;
}else
{
//int o=0;
InputFile.read((char*)&h,sizeof(h));

while(!InputFile.eof())
{
Vh.push_back(h);
cout<<maxhotelcode;
maxhotelcode++;
InputFile.read((char*)&h,sizeof(h));

}
InputFile.close();
InputFile.clear();


}


cout << " ADD NEW HOTEL DETAILS" << endl;
cout << "New Hotel Code is:"<<maxhotelcode<<endl;



OutputFile.open(filename,ios::binary|ios::out);


char reply='Y';



h.hotel_code=maxhotelcode;
maxhotelcode++;
cout << "Enter Hotel/Resort name:" << endl;
cin >>h.hotel_name;
cout << "Enter City name:" << endl;
cin >> h.hotel_city;
cout << "Enter the number of Regular rooms:" << endl;
cin >> h.available_regular_rooms;
cout << "Enter the tariff for Regular rooms:" << endl;
cin >> h.tariff_regular_room;
cout << "Enter the number of Deluxe rooms:" << endl;
cin >> h.available_deluxe_rooms;
cout << "Enter the tariff for Deluxe rooms:" << endl;
cin >> h.tariff_deluxe_room;

Vh.push_back(h);



for(int n=0;n<Vh.size();n++){
//cout<<Vh[n].hotel_code<<endl;
//cout<<Vh[n].hotel_name<<endl;
//cout<<Vh[n].hotel_city<<endl;
OutputFile.write((char*)&Vh[n],sizeof(Vh[n]));//这里当你第一次运行的时候其实只有一条纪录,可是你写如两次!!!为什么呢?那是因为你定义的时候Vh(1),已经有一纪录了,你再push_back就是二了,只需要把这里改成Vh!!!!!!!!
}


OutputFile.close();
OutputFile.clear();
dispMenu();

}

[1982pc]

void addNewHotel(char *filename)
{
system("cls");
ofstream OutputFile;
ifstream InputFile;
vector<Hotel> Vh(1);
Hotel h;
int maxhotelcode=1;
int hotelcode;
InputFile.open(filename,ios::binary|ios::in);

if(!InputFile){

hotelcode=1;
}else
{
//int o=0;
InputFile.read((char*)&h,sizeof(h));

while(!InputFile.eof())
{
Vh.push_back(h);
cout<<maxhotelcode;
maxhotelcode++;
InputFile.read((char*)&h,sizeof(h));

}
InputFile.close();
InputFile.clear();


}


cout << " ADD NEW HOTEL DETAILS" << endl;
cout << "New Hotel Code is:"<<maxhotelcode<<endl;



OutputFile.open(filename,ios::binary|ios::out);


char reply='Y';



h.hotel_code=maxhotelcode;
maxhotelcode++;
cout << "Enter Hotel/Resort name:" << endl;
cin >>h.hotel_name;
cout << "Enter City name:" << endl;
cin >> h.hotel_city;
cout << "Enter the number of Regular rooms:" << endl;
cin >> h.available_regular_rooms;
cout << "Enter the tariff for Regular rooms:" << endl;
cin >> h.tariff_regular_room;
cout << "Enter the number of Deluxe rooms:" << endl;
cin >> h.available_deluxe_rooms;
cout << "Enter the tariff for Deluxe rooms:" << endl;
cin >> h.tariff_deluxe_room;

Vh.push_back(h);



for(int n=0;n<Vh.size();n++){
//cout<<Vh[n].hotel_code<<endl;
//cout<<Vh[n].hotel_name<<endl;
//cout<<Vh[n].hotel_city<<endl;
OutputFile.write((char*)&Vh[n],sizeof(Vh[n]));//这里当你第一次运行的时候其实只有一条纪录,可是你写如两次!!!为什么呢?那是因为你定义的时候Vh(1),已经有一纪录了,你再push_back就是二了,只需要把这里改成Vh!!!!!!!!
}


OutputFile.close();
OutputFile.clear();
dispMenu();

}

[didoleo]

to:1982pc()
谢谢1982pc() 老兄

我们老师太变态了,一定要用Vector,上课又只会读课本,又没例子.

vector<Hotel> Vh(1);这样是定义了一个只有能容纳一个元素的数组,但这个元素是空的.
vector的好处就是他会随着记录的增加自动扩大容量.我定义vector<Hotel> Vh(100)也可以
他只表明了他的容量,就象 int intArr[100],这个intArr里面没东西的,除非我给他们都赋值.


你能不能给我一个完整一点的代码让我学一下呢?

功能就是录入hotel的信息,每个hotel要给他编个码,就用int型好了,每个hotel信息当成一条记录,存放到文件hotel.dat里,要用vector.

谢谢.分不够再加

[didoleo]

自己up一下,下午来看.

[WuYL7812]

vector<Hotel> Vh(1);
这条语句错了，应该是 vector<Hotel> Vh;
用默认参数

[WuYL7812]

你用vector<Hotel> Vh(1);时Vh里面已经有一个元素了，此元素是用Hotel得默认构造函数构造形成的，当然是乱码。以后条用push_back是不会把添加的元素放到已经有的内容里的。

[ghostsG]

up

[zengwujun]

//楼主看来对vector的capacity和size混淆不清
//capacity:容量
//size:已站容量
//vector<int> coll(2);//<--分配两个元素，如果capacity不够，倍增
//coll.reserve()//<--改变容量
//coll.resize(3);//<--改变已站容量
//coll.empty();//<--依据size()进行判断,size()为0返回true;

看看这个例子，体会体会
#include <vector>
#include <stdio.h>
using namespace std;

void main()
{
vector<int> coll(2);
printf("capacity=%d,size=%d\n",coll.capacity(),coll.size());
coll.push_back(1);
printf("capacity=%d,size=%d\n",coll.capacity(),coll.size());
coll.push_back(2);
coll.reserve(10);
printf("capacity=%d,size=%d\n",coll.capacity(),coll.size());
coll.push_back(3);
printf("capacity=%d,size=%d\n",coll.capacity(),coll.size());
coll.push_back(4);
coll.resize(3);
printf("capacity=%d,size=%d\n",coll.capacity(),coll.size());
coll.push_back(5);
printf("capacity=%d,size=%d\n",coll.capacity(),coll.size());
coll.push_back(6);
}