HashSetMy

class HashSetMy<T> : IEnumerable<T>
    {
        private const int MIN_BUFFER_SIZE = 16;
        private const int RESIZE_FACTOR = 2;
        private const double FULL_FACTOR = 0.7;

        private List<T>[] buffer;


        public int Count { get; private set; }
        public HashSetMy(int size = MIN_BUFFER_SIZE)
        {
            buffer = new List<T>[size];
            this.Count = 0;
        }

        public bool AddItem(T value)
        {
            var hash = (uint)value.GetHashCode();
            var index = hash % buffer.Length;

            var existed = buffer[index] != null && buffer[index].Contains(value);

            if (existed)
            {
                return false;
            }
            if (buffer[index] == null)
            {
                buffer[index] = new List<T>();
            }
            buffer[index].Add(value);
            this.Count++;
            if ((double)this.Count / buffer.Length > FULL_FACTOR)
            {
                this.Resize(buffer.Length * RESIZE_FACTOR);
            }
            return true;
        }

        public bool Contains(T value)
        {
            var hash = (uint)value.GetHashCode();
            var index = hash % buffer.Length;

            return buffer[index] != null && buffer[index].Contains(value);
        }

        public bool Remove(T value)
        {
            var hash = (uint)value.GetHashCode();
            var index = hash % buffer.Length;
            if (buffer[index] == null)
            {
                return false;
            }

            return this.buffer[index].Remove(value);
        }

        private void Resize(int newSize)
        {
            var newBuffer = new List<T>[newSize];

            foreach (var x in this)
            {
                var hash = (uint)x.GetHashCode();
                var index = hash % newSize;
                if (newBuffer[index] == null)
                {
                    newBuffer[index] = new List<T>();
                }
                newBuffer[index].Add(x);
            }
            this.buffer = newBuffer;
        }

        public IEnumerator<T> GetEnumerator()
        {
            foreach (var list in buffer)
            {
                if (list == null)
                {
                    continue;
                }
                foreach (var x in list)
                {
                    yield return x;
                }
            }
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return this.GetEnumerator();
        }
    }