[C#] Generic Collection 구현 해보기

* List<T> 구현

 

public class MyList<T> : IEnumerable<T>, IEnumerable
{
    private T[] data;
    private int capacity;
    private int count;

    // interface start
    IEnumerator<T> IEnumerable<T>.GetEnumerator() { return new MyList<T>.Enumerator(this, count); }
    IEnumerator IEnumerable.GetEnumerator() { return new MyList<T>.Enumerator(this, count); }
    // interface end

    public int Capacity { get { return capacity; } }
    public int Count { get { return count; } }

    public MyList(int capacity)
    {
        this.data = new T[capacity];
        this.capacity = capacity;
    }

    public T this[int index] 
    { 
        get
        {
            return data[index];
        }

        set
        {
            data[index] = value;
        }
    }

    public void Add(T item)
    {
        if (capacity <= count)
        {
            int newCapacity = capacity * 2;
            Array.Resize<T>(ref data, newCapacity);

            Console.WriteLine($"Resized : [{capacity}] -> [{newCapacity}]");
            capacity = newCapacity;
        }

        data[count++] = item;
    }

    public void Clear()
    {
        Array.Resize<T>(ref data, 0);
        capacity = 0;
        count = 0; 
    }


    public struct Enumerator : IEnumerator<T>, IEnumerator
    {
        private MyList<T> parent;
        private int count;
        private int position;

        // interface start
        T IEnumerator<T>.Current { get { return parent[position]; } }
        object IEnumerator.Current { get { return parent![position]!; } }

        public bool MoveNext()
        {
            ++position;
            if(position >= count)
            {
                return false;
            }

            return true;
        }

        public void Reset() { position = -1; }
        public void Dispose() { Reset(); }
        // interface end

        public Enumerator(MyList<T> parent, int count)
        {
            this.parent = parent;
            this.count = count;
            this.position = -1;
        }
    }
}