using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace s
{
    class Program
    {
        static Int64 sumValue = 0;
        static List<int> randomList = new List<int>();
        static Semaphore sem = new Semaphore(1, 1);

        static void AddToResult(int toAdd)
        {
            sem.WaitOne();
            sumValue += toAdd;
            sem.Release();
        }
        static void FillList(int Length)
        {
            var rand = new Random();
            for (int i = 0; i < Length; i++)
            {
                randomList.Add(rand.Next(1, 5000));
            }
        }

        static void PartialSum(int Index, int ToSum)
        {
            int sum = 0;
            int range = Index + ToSum;

            for (int i = Index; i < range; i++)
            {
                sum += randomList[i];
            }

            AddToResult(sum);
        }

        static List<int> SetChunk(int AmmontOfThreads)
        {
            if (AmmontOfThreads == 0)
                throw new Exception("Ammount of Threads cannot be zero");

            List<int> chunks = new List<int>();
            int toCover = randomList.Count;
            double ch = randomList.Count / AmmontOfThreads;

            for (int i = 0; i < AmmontOfThreads; i++)
            {
                if (i == AmmontOfThreads - 1)
                {
                    chunks.Add(toCover);
                }
                else
                {
                    int p = (int)Math.Floor(ch);
                    chunks.Add(p);
                    toCover -= p;
                }
            }

            return chunks;
        }

        static private List<int> SetIndexes(List<int> Chunks)
        {
            var listOfIndex = new List<int>();
            int currentIndex = 0;
            foreach (int chunk in Chunks)
            {
                listOfIndex.Add(currentIndex);
                currentIndex += chunk;
            }

            return listOfIndex;
        }
        static private List<Thread> SetThreads(List<int> listOfIndex,List<int> Chunks)
        {
            var threadList = new List<Thread>();

            for (int i = 0; i < listOfIndex.Count; i++)
            {
                int localIndex = i;
                var t = new Thread(() => PartialSum(listOfIndex[localIndex], Chunks[localIndex]));
                t.Start();
                threadList.Add(t);
            }

            return threadList;
        }

        static void Main(string[] args)
        {
            const int arraySize = 10000;
            const int numberOfThreads = 5;

            var Chunks = SetChunk(10);           
            FillList(arraySize);
            Chunks = SetChunk(numberOfThreads);
            List<int> listOfIndex = SetIndexes(Chunks);
            List<Thread> threadList = SetThreads(listOfIndex, Chunks);
           
            foreach (var t in threadList)
                t.Join();

            Console.WriteLine("Wielowątkowo: ");
            Console.WriteLine(sumValue);
            Console.WriteLine("Sekwencyjnie: ");
            Console.WriteLine(randomList.Sum());
        }

        
    }
}