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  1. #include <stdio.h>
  2. #include <string.h>
  3.  
  4. #define MAX_USERS 10
  5. #define MAX_USERNAME_LENGTH 20
  6. #define MAX_PASSWORD_LENGTH 20
  7.  
  8. struct User {
  9.     char username[MAX_USERNAME_LENGTH];
  10.     char password[MAX_PASSWORD_LENGTH];
  11. };
  12.  
  13. struct User users[MAX_USERS];
  14. int numUsers = 0;
  15.  
  16. int registerUser(char username[], char password[]) {
  17.     if (numUsers >= MAX_USERS) {
  18.         printf("Cannot register more users. Maximum limit reached.\n");
  19.         return 0;
  20.     }
  21.  
  22.     // Check if username already exists
  23.     for (int i = 0; i < numUsers; i++) {
  24.         if (strcmp(users[i].username, username) == 0) {
  25.             printf("Username already exists. Please choose a different username.\n");
  26.             return 0;
  27.         }
  28.     }
  29.  
  30.     // Add user
  31.     strcpy(users[numUsers].username, username);
  32.     strcpy(users[numUsers].password, password);
  33.     numUsers++;
  34.     printf("User registered successfully.\n");
  35.     return 1;
  36. }
  37.  
  38. int loginUser(char username[], char password[]) {
  39.     for (int i = 0; i < numUsers; i++) {
  40.         if (strcmp(users[i].username, username) == 0 && strcmp(users[i].password, password) == 0) {
  41.             printf("Login successful. Welcome, %s!\n", username);
  42.             return 1;
  43.         }
  44.     }
  45.     printf("Invalid username or password. Please try again.\n");
  46.     return 0;
  47. }
  48.  
  49. int main() {
  50.     // Example usage
  51.     registerUser("user1", "password123");
  52.     registerUser("user2", "abc456");
  53.  
  54.     loginUser("user1", "password123"); // Successful login
  55.     loginUser("user2", "wrongpass");  // Unsuccessful login
  56.  
  57.     return 0;
  58. }
  59.  
Success #stdin #stdout 0.01s 5304KB
comments (?)
stdin 
Standard input is empty
stdout 
User registered successfully.
User registered successfully.
Login successful. Welcome, user1!
Invalid username or password. Please try again.
https://ideone.com/1DK0ou
language:
C (gcc 8.3)
created:
11 days ago
visibility:
public

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