为什么读出来的输出结果多一个？求教 - 编程论坛

#2

rjsp2016-11-01 08:54

程序代码：

#include <iostream>
#include <string>

class Student
{
    friend std::istream& operator>>( std::istream&, Student& );
    friend std::ostream& operator<<( std::ostream&, const Student& );

public:
    Student() : stuno_(0),classno_(0),cscore_(0),pscore_(0),tscore_(0)
    {
    }

    double avgscore() const
    {
        return (cscore_+pscore_+tscore_)/3;
    }
private:
    int stuno_, classno_;
    std::string name_;
    double cscore_, pscore_, tscore_;
};

using namespace std;

istream& operator>>( istream& is, Student& s )
{
    return is >> s.stuno_ >> s.name_ >> s.classno_ >> s.cscore_ >> s.pscore_ >> s.tscore_;
}
ostream& operator<<( ostream &os, const Student& s )
{
    return os << s.stuno_ << ' ' << s.name_ << ' ' << s.classno_ << ' ' << s.cscore_ << ' ' << s.pscore_ << ' ' << s.tscore_;
}

#include <fstream>
#include <vector>

int main( void )
{
    vector<Student> s;
    {
        ifstream in("Text.txt");
        for( Student a; in>>a; )
            s.push_back( a );
    }
    {
        ofstream out("Text1.txt");
        for( vector<Student>::const_iterator itor=s.begin(); itor!=s.end(); ++itor )
            out << *itor << '\n';
    }
    return 0;
}

主要错在
while (in)
{
in >> a;
s.push_back(a); // 上一句未必读成功
}

#3

starlz2016-11-01 09:36

谢谢楼上，我上网查了一下改成这样也可以：）
    vector<Students>s;
    Students a;
    ifstream in;
    in.open("Text.txt");
while (!in.eof())
        {
            in >> a;
            s.push_back(a);
        }
    in.close();

#4

rjsp2016-11-01 14:08

以下是引用starlz在2016-11-1 09:36:43的发言：

谢谢楼上，我上网查了一下改成这样也可以：）
    vectors;
    Students a;
    ifstream in;
    in.open("Text.txt");
while (!in.eof())
        {
            in >> a;
            s.push_back(a);
        }
    in.close();

不可以