sliding_window.dart

import 'package:flutter/material.dart';
import 'dart:math';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Design Pattern Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const SlidingWindowScreen(),
    );
  }
}

class SlidingWindowScreen extends StatefulWidget {
  const SlidingWindowScreen({Key? key}) : super(key: key);

  @override
  SlidingWindowScreenState createState() => SlidingWindowScreenState();
}

class SlidingWindowScreenState extends State<SlidingWindowScreen>
    with SingleTickerProviderStateMixin {
  List<int> numbers = [];
  final int k = 3;
  late AnimationController _animationController;
  late Animation<Offset> _animation;
  List<int> maxSumElements = [];

  @override
  void initState() {
    super.initState();
    generateNumbers();
    _animationController = AnimationController(
      vsync: this,
      duration: const Duration(milliseconds: 500),
    );
    _animation = Tween<Offset>(begin: Offset.zero, end: const Offset(0.0, 1.0))
        .animate(_animationController);
  }

  @override
  void dispose() {
    _animationController.dispose();
    super.dispose();
  }

  void generateNumbers() {
    final random = Random();
    numbers = List.generate(10, (_) => random.nextInt(10));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Sliding Window - bwnyasse.net'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text(
              'Numbers:',
              style: TextStyle(fontSize: 18),
            ),
            const SizedBox(height: 10),
            buildNumberList(),
            const SizedBox(height: 20),
            SlideTransition(
              position: _animation,
              child: Text(
                'Max Sum of $k Consecutive Elements: ${findMaxSum()}',
                style:
                    const TextStyle(fontSize: 24, fontWeight: FontWeight.bold),
              ),
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            generateNumbers();
            maxSumElements.clear();
          });
        },
        child: const Icon(Icons.play_arrow),
      ),
    );
  }

  Widget buildNumberList() {
    return SizedBox(
      height: 40,
      child: ListView.builder(
        shrinkWrap: true,
        scrollDirection: Axis.horizontal,
        itemCount: numbers.length,
        itemBuilder: (BuildContext context, int index) {
          final color =
              maxSumElements.contains(index) ? Colors.green : Colors.blue;
          return Container(
            width: 40,
            height: 40,
            margin: const EdgeInsets.symmetric(horizontal: 4),
            decoration: BoxDecoration(
              color: color,
              borderRadius: BorderRadius.circular(8),
            ),
            child: Center(
              child: Text(
                numbers[index].toString(),
                style: const TextStyle(color: Colors.white),
              ),
            ),
          );
        },
      ),
    );
  }

  int findMaxSum() {
    int maxSum = 0;
    int currentSum = 0;
    int maxSumIndex = 0;

    // Calculate sum of first 'k' elements
    for (int i = 0; i < k; i++) {
      currentSum += numbers[i];
    }

    maxSum = currentSum;

    // Slide the window by one element at a time
    for (int i = k; i < numbers.length; i++) {
      currentSum = currentSum - numbers[i - k] + numbers[i];
      if (currentSum > maxSum) {
        maxSum = currentSum;
        maxSumIndex = i - k + 1;
      }
    }

    maxSumElements = List<int>.generate(k, (index) => maxSumIndex + index);

    return maxSum;
  }
}