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  1. #include <iostream>
  2. #include <string>
  3. #include <fstream>
  4.  
  5. using namespace std;
  6.  
  7. struct User {
  8.     string username;
  9.     string password;
  10. };
  11.  
  12. // Function to register a new user
  13. void registerUser() {
  14.     User newUser;
  15.     cout << "Enter username: ";
  16.     cin >> newUser.username;
  17.     cout << "Enter password: ";
  18.     cin >> newUser.password;
  19.  
  20.     ofstream file("users.txt", ios::app);
  21.     file << newUser.username << ":" << newUser.password << endl;
  22.     file.close();
  23.  
  24.     cout << "Registration successful!" << endl;
  25. }
  26.  
  27. // Function to login an existing user
  28. void loginUser() {
  29.     string username, password;
  30.     cout << "Enter username: ";
  31.     cin >> username;
  32.     cout << "Enter password: ";
  33.     cin >> password;
  34.  
  35.     ifstream file("users.txt");
  36.     string line;
  37.     bool found = false;
  38.  
  39.     while (getline(file, line)) {
  40.         size_t colonPos = line.find(":");
  41.         string storedUsername = line.substr(0, colonPos);
  42.         string storedPassword = line.substr(colonPos + 1);
  43.  
  44.         if (username == storedUsername && password == storedPassword) {
  45.             found = true;
  46.             break;
  47.         }
  48.     }
  49.  
  50.     file.close();
  51.  
  52.     if (found) {
  53.         cout << "Login successful!" << endl;
  54.     } else {
  55.         cout << "Invalid username or password." << endl;
  56.     }
  57. }
  58.  
  59. int main() {
  60.     int choice;
  61.     cout << "1. Register" << endl;
  62.     cout << "2. Login" << endl;
  63.     cout << "Enter your choice: ";
  64.     cin >> choice;
  65.  
  66.     if (choice == 1) {
  67.         registerUser();
  68.     } else if (choice == 2) {
  69.         loginUser();
  70.     } else {
  71.         cout << "Invalid choice." << endl;
  72.     }
  73.  
  74.     return 0;
  75. }
Success #stdin #stdout 0.01s 5284KB
comments (?)
stdin 
Standard input is empty
stdout 
1. Register
2. Login
Enter your choice: Invalid choice.
https://ideone.com/vWu8ap
language:
C++ (gcc 8.3)
created:
10 days ago
visibility:
public

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