Smart Home Automation
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import 'dart:io';

void main() {
  const int minTemp = 15;
  const int maxTemp = 30;

  bool lightsOn = false;
  int temperature = 20;
  bool securityArmed = false;

  while (true) {
    print('\n=== Smart Home Automation System ===');
    print('1. Turn Lights On/Off');
    print('2. Set Thermostat Temperature');
    print('3. Arm/Disarm Security System');
    print('4. View System Status');
    print('5. Exit');
    stdout.write('Choose an option: ');
    String? choice = stdin.readLineSync();

    if (choice == '5') {
      print('Exiting Smart Home System... Goodbye!');
      break;
    }

    switch (choice) {
      case '1':
        lightsOn = !lightsOn;
        print('Lights turned ${lightsOn ? "ON" : "OFF"}');
        break;

      case '2':
        stdout.write('Enter temperature ($minTemp - $maxTemp): ');
        int? newTemp = int.tryParse(stdin.readLineSync()!);
        if (newTemp != null && newTemp >= minTemp && newTemp <= maxTemp) {
          temperature = newTemp;
          print('Temperature set to $temperature°C');
        } else {
          print('Invalid temperature! Must be between $minTemp and $maxTemp.');
        }
        break;

      case '3':
        securityArmed = !securityArmed;
        print('Security system is now ${securityArmed ? "ARMED" : "DISARMED"}');
        break;

      case '4':
        print('\n--- System Status ---');
        print('Lights: ${lightsOn ? "ON" : "OFF"}');
        print('Thermostat: $temperature°C');

        if (temperature % 3 == 0 && temperature % 5 == 0) {
          print('Perfect Day');
        } else if (temperature % 3 == 0) {
          print('Cool Day');
        } else if (temperature % 5 == 0) {
          print('Warm Day');
        }

        print('Security System: ${securityArmed ? "ARMED" : "DISARMED"}');
        break;

      default:
        print('Invalid option. Please try again.');
    }
  }
}


Budget Management Application
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import 'dart:io';

void main() {
  List<Map<String, double>> incomeList = [];
  List<Map<String, double>> expenseList = [];

  while (true) {
    print('\n=== Budget Management Application ===');
    print('1. Add Income');
    print('2. Add Expense');
    print('3. View Summary');
    print('4. Exit');
    stdout.write('Choose an option: ');
    String? choice = stdin.readLineSync();

    if (choice == '4') {
      print('Exiting Budget Manager... Goodbye!');
      break;
    }

    switch (choice) {
      case '1':
        stdout.write('Enter income description: ');
        String? desc = stdin.readLineSync();
        stdout.write('Enter income amount: ');
        double? amount = double.tryParse(stdin.readLineSync()!);

        if (amount != null && amount > 0) {
          incomeList.add({desc ?? 'Income': amount});
          print('Income added successfully.');
        } else {
          print('Invalid amount. Please enter a positive number.');
        }
        break;

      case '2':
        stdout.write('Enter expense description: ');
        String? desc = stdin.readLineSync();
        stdout.write('Enter expense amount: ');
        double? amount = double.tryParse(stdin.readLineSync()!);

        if (amount != null && amount > 0) {
          expenseList.add({desc ?? 'Expense': amount});
          print('Expense added successfully.');
        } else {
          print('Invalid amount. Please enter a positive number.');
        }
        break;

      case '3':
        double totalIncome = 0;
        double totalExpense = 0;

        for (var i in incomeList) {
          totalIncome += i.values.first;
        }
        for (var e in expenseList) {
          totalExpense += e.values.first;
        }

        double net = totalIncome - totalExpense;
        print('\n--- Summary ---');
        print('Total Income: \$${totalIncome.toStringAsFixed(2)}');
        print('Total Expenses: \$${totalExpense.toStringAsFixed(2)}');

        if (net > 0) {
          double tax = net * 0.15;
          print('Your net profit is \$${net.toStringAsFixed(2)}');
          print('Tax to be paid (15%): \$${tax.toStringAsFixed(2)}');
        } else if (net < 0) {
          print('Your net loss is \$${net.abs().toStringAsFixed(2)}');
        } else {
          print('You broke even — no profit, no loss.');
        }
        break;

      default:
        print('Invalid option. Please try again.');
    }
  }
}