MyHashMap.cs

//https://leetcode.com/problems/design-hashmap

namespace LeetCode.Problems;

public sealed class MyHashMap : ProblemBase
{
    [Theory]
    [ClassData(typeof(MyHashMap))]
    public override void Test(object[] data) => base.Test(data);

    protected override void AddTestCases()
        => Instructions<HashMap, int[]>(config =>
            config
                .MapConstructor("MyHashMap")
                .MapInstruction("put", (it, data) => it.Put(data[0], data[1]))
                .MapInstruction("get", (it, data) => it.Get(data[0]))
                .MapInstruction("remove", (it, data) => it.Remove(data[0]))
        )
        .Add(it => it.Data<int>("""[[], [1, 1], [2, 2], [1], [3], [2, 1], [2], [2], [2]]""")
                     .Instructions("""["MyHashMap", "put", "put", "get", "get", "put", "get", "remove", "get"]""")
                     .Output("[null, null, null, 1, -1, null, 1, null, -1]"));

    public class HashMap
    {
        class Data
        {
            public int Key;
            public int Value;
        }

        private readonly LinkedList<Data>?[] _data = new LinkedList<Data>?[1000];

        public void Put(int key, int value)
        {
            var index = key % _data.Length;

            _data[index] ??= new LinkedList<Data>();

            var node = _data[index]!.First;
            while (node != null)
            {
                if (node.Value.Key == key)
                {
                    node.Value.Value = value;
                    return;
                }

                node = node.Next;
            }

            _data[index]!.AddFirst(new Data {Key = key, Value = value});
        }

        public int Get(int key)
        {
            var node = GetNode(key);
            return node != null ? node.Value.Value : -1;
        }

        public void Remove(int key)
        {
            var node = GetNode(key);
            if (node != null)
            {
                _data[key % _data.Length]!.Remove(node);
            }
        }

        private LinkedListNode<Data>? GetNode(int key)
        {
            var node = _data[key % _data.Length]?.First;
            while (node != null)
            {
                if (node.Value.Key == key)
                {
                    return node;
                }

                node = node.Next;
            }

            return null;
        }
    }
}