Answer to Question #42792 in C++ for ahmed

Question

Program asks user to enter user name and password
If same user name exists in the primary index file, program does nothing and prints "User name already exist".
Otherwise, a new record is created of type admin, and written to "users.dat" file in fixed length record structure and the primary index file is updated .

Answer 1

#include<iostream>
#include<string>
#include<fstream>
#include<list>
#include<algorithm>
 
using namespacestd;
 
// filenames
conststring fnindex = "index.dat";
conststring fnusers = "users.dat";
 
// list of usernames
list<string>users;
 
boolAddUser (string username,string password) {
    ofstream findex(fnindex,ios::app);
    ofstream fusers(fnusers,ios::app);
    string output;
    bool res = true;
 
    // primary index file is updated
    if (findex.is_open()) {
        output =username + "\n";
        findex <<output;
        findex.close();
    } else {
        res = false;
    }
    
    // new record is written"users.dat"
    if (fusers.is_open()) {
        output =username + "|" + "admin" + "|" +password + "\n";
        fusers <<output;
        fusers.close();
    } else {
        res = false;
    }
 
    returnres;
}
 
boolLoadUsernames() {
    ifstream findex(fnindex);
    string username;
 
    // users are added to usernamelist
    if (findex.is_open()) {
        while (getline(findex,username)) {
            users.push_back(username);
        }
        findex.close();
        return true;
    } else {
        return false;
    }
}
 
intmain() {
    list<string>::iteratorpos;
    
    string username;
    string password;
    bool newUser = true;
 
    LoadUsernames();
 
    while (newUser) {
        cout << "Enterusername:" << endl;
        cin >>username;
 
        cout << "Enterpassword:" << endl;
        cin >>password;
 
        //username is checked 
        pos =find(users.begin(),users.end(),username);
        if (pos== users.end()) {
            AddUser(username,password);
            newUser = false;
        } else {
            cout << "Username already exist" << endl;
        }
    }   
 
    return 0;
}