file processing, delete certain data

would anyone help me to settle this function?
for your information, i want to delete certain information from the database.

example in the the database is name, address, and room number
i just want to edit the room number of certain person from the database, anyone who know how to do that please tell me later.

thanx in advance.

Code:

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void buyticket(int m){

        fstream ticket("cruise.dat", ios::in | ios::out); //open patient's file
        if(!ticket)
        {
                cout<<"File could not be opened to read."<<endl;
                exit(1);
        }
        ticket.seekg(0);
        ship data;

        ticket.seekg(  (m-1) * sizeof(ship)  );
        ticket.read((char *)&data, sizeof(ship));
        cout<<"Available ticket : "<< data.return_room() <<endl;


               
                int avalroom,befroom;
                cout<<"Enter room : "<<endl;
                cin>>avalroom;
                befroom=data.return_room();

                room=befroom-avalroom;

                cout<<"After : "<<room<<endl<<endl;

                ticket.seekp(  (m-1) * sizeof(ship)  );
                ticket.write((char *)&data,sizeof(ship));//write into the binary file
                cout<<"Record Modified!"<<endl;

        ticket.close();
        getch();
}

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What you should do IMO is create a class or a struct with all the data you need for the person. Read everything into an array or a std::vector, change it there, and then overwrite the file with the modified data.