C++ 根据ID/注册搜索和编辑.txt fstream文件

我试图从.txt中搜索特定的ID/注册，并相应地显示相应的信息。在这种情况下，我希望根据应输入的相应注册号显示定价

读和写文件不是我的问题。网上有很多关于阅读和写作的信息，但根据ID/注册进行搜索和显示的信息不多

#include <iostream>
#include <iomanip>
#include <fstream>
#include <cstdlib>
#include <string>

using namespace std;

int main()
{
    string line;
    double cost;
    string reg;

    ifstream in_stream;
    ofstream out_stream;

    char registration[10]; 

    //Open file
    in_stream.open("Fines.dat");

    //Error if opening fails
    if (in_stream.fail())
    {
        cout << "Input file could not open. " << endl;
        exit(1);
    }

    //Open out stream file
    out_stream.open("OutStandingFines.dat");

    //Error if opening fails
    if (out_stream.fail())
    {
        cout << "Output file opening failed.\n";
        exit(1);
    }

    //Display original .dat file
    cout <<"Original .dat File" << endl;
    if(in_stream.is_open())
    {
        while(in_stream >> reg >> cost)
        {       
                cout << reg <<" " << cost << '\n';

        }
        in_stream.close();
    }
    else
    {
        cout <<"File is not open: " << endl;
    }



/////////////My problem is from here//////////////////////////

    //Enter the registration number you wish to search
    cout << "Please enter registration number: " << endl;
    cin >>registration;



//I must display all cost values that have the same registration number???????? I need help with this
/*
    for (int i = 0; i < 10; i++)
    {


                if( reg == registration)
                {   

                    cout << fixed << setw(2)<< setprecision(2) <<"R " << cost << '\n';
                    out_stream << fixed << setw(2)<< setprecision(2) << "R "<< cost << endl; //send back to .dat
                }


    }

*/




    in_stream.close();
    out_stream.close();

    system("pause");
    return(0);
}

---

好的，我设法得到了输出。现在的问题是显示具有相同注册/ID的所有值

由于某些原因，当我输入ABC123时，只显示fstream.txt中的最后一行

txt包含以下信息。

---

只需按照添加了if语句的代码中更高的方式读取文件？您可能还想考虑将数据加载到内存或使用某种类型的数据库，但进入这一点有点超出评论/答案的范围。

ABC123 400
DEC234 340
ABC123 500
GED345 600
ABC123 240
GEE600 120
GED345 230
GEE600 470
ABC123 120

#include <iostream>
#include <iomanip>
#include <fstream>
#include <cstdlib>
#include <string>

using namespace std;

int main()
{

    string line;
    double cost;
    string reg;

    ifstream in_stream;
    ofstream out_stream;

    string registration; 


    in_stream.open("Fines.dat");

    if (in_stream.fail())
    {
        cout << "Input file could not open. " << endl;
        exit(1);
    }

    out_stream.open("OutStandingFines.dat");
    if (out_stream.fail())
    {
        cout << "Output file opening failed.\n";
        exit(1);
    }

    //Display original .dat file
    cout <<"Original .dat File" << endl;
    if(in_stream.is_open())
    {
        while(in_stream >> reg >> cost)
        {       
                cout << reg <<" " << cost << '\n';
        }

    }
    else
    {
        cout <<"File is not open: " << endl;
    }



    //Enter Registration here
    cout << "Please enter registration number: " << endl;
    cin >>registration;

    //compare and display all registration numbers that match
    cout <<"Fines: " << endl;
    if(out_stream.is_open())
    {

        while(reg == registration)
        {       


                cout << fixed << setw(2)<< setprecision(2) <<"R " << cost << '\n';
                out_stream << fixed << setw(2)<< setprecision(2) << "R "<< cost << endl; //send back to .dat

            exit(1);
        }
    }
    else
    {
        cout <<"File is not open: " << endl;
    }



    in_stream.close();
    out_stream.close();

    system("pause");
    return(0);
}