Smart Home Automation System - Dart Solution
----------------------------------------------

import 'dart:io';

const int minTemp = 15;
const int maxTemp = 30;

void main() {
  bool lightsOn = false;
  int thermostat = 20;
  bool securityArmed = false;

  while (true) {
    print("\n=== Smart Home Automation ===");
    print("1. Toggle Lights");
    print("2. Set Thermostat");
    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 == "1") {
      lightsOn = !lightsOn;
      print("Lights are now: ${lightsOn ? "ON" : "OFF"}");
    } else if (choice == "2") {
      stdout.write("Enter temperature ($minTemp-$maxTemp): ");
      String? tempInput = stdin.readLineSync();
      int? temp = int.tryParse(tempInput ?? "");

      if (temp != null && temp >= minTemp && temp <= maxTemp) {
        thermostat = temp;
        print("Thermostat set to $thermostat°C");
      } else {
        print("Invalid temperature.");
      }
    } else if (choice == "3") {
      securityArmed = !securityArmed;
      print("Security system is now: ${securityArmed ? "ARMED" : "DISARMED"}");
    } else if (choice == "4") {
      String lightStatus = lightsOn ? "ON" : "OFF";
      String securityStatus =
          securityArmed ? "ARMED".toUpperCase() : "DISARMED".toUpperCase();

      String tempMessage = "";
      if (thermostat % 3 == 0 && thermostat % 5 == 0) {
        tempMessage = "Perfect Day";
      } else if (thermostat % 3 == 0) {
        tempMessage = "Cool Day";
      } else if (thermostat % 5 == 0) {
        tempMessage = "Warm Day";
      }

      print("\n--- System Status ---");
      print("Lights: $lightStatus");
      print("Thermostat: $thermostat°C $tempMessage");
      print("Security System: $securityStatus");
    } else if (choice == "5") {
      print("Exiting system...");
      break;
    } else {
      print("Invalid choice.");
    }
  }
}

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Budget Management System - Dart Solution
-------------------------------------------------------

import 'dart:io';

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

  while (true) {
    print("\n=== Budget Management ===");
    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 == "1") {
      stdout.write("Income description: ");
      String desc = stdin.readLineSync() ?? "";

      stdout.write("Amount: ");
      double? amount = double.tryParse(stdin.readLineSync() ?? "");

      if (amount != null && amount >= 0) {
        incomeList.add({desc: amount});
        print("Income added.");
      } else {
        print("Invalid amount.");
      }
    } else if (choice == "2") {
      stdout.write("Expense description: ");
      String desc = stdin.readLineSync() ?? "";

      stdout.write("Amount: ");
      double? amount = double.tryParse(stdin.readLineSync() ?? "");

      if (amount != null && amount >= 0) {
        expenseList.add({desc: amount});
        print("Expense added.");
      } else {
        print("Invalid amount.");
      }
    } else if (choice == "3") {
      double incomeTotal = 0;
      double expenseTotal = 0;

      incomeList.forEach((item) => incomeTotal += item.values.first);
      expenseList.forEach((item) => expenseTotal += item.values.first);

      double net = incomeTotal - expenseTotal;

      print("\n--- Summary ---");
      print("Total Income: \$${incomeTotal}");
      print("Total Expenses: \$${expenseTotal}");
      print(net >= 0
          ? "Your net profit is \$${net}"
          : "Your net loss is \$${net.abs()}");

      double tax = net > 0 ? net * 0.15 : 0;
      if (tax > 0) {
        print("Tax to be paid: \$${tax}");
      }
    } else if (choice == "4") {
      print("Exiting...");
      break;
    } else {
      print("Invalid choice.");
    }
  }
}