Question

i have this collection and i want to sort it based on rating then remove the duplicate name based on the nearest spelling distance using Levenshtein Algorithm..

here’s my code so far

and my expected result is

 /* 
  * Expected result:
  * 
  * Jjamppong v2
  * Maggi
  * Quick Chow
  * 
  */

---

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Item> _items = new List<Item>();

            _items.Add(new Item() { ItemID = 1, Name = "Jjamppong", Rating = 4 });
            _items.Add(new Item() { ItemID = 2, Name = "Jjamppong v2", Rating = 6 });
            _items.Add(new Item() { ItemID = 3, Name = "Jjamppong v3", Rating = 3 });
            _items.Add(new Item() { ItemID = 4, Name = "Jjamppong v4", Rating = 2 });
            _items.Add(new Item() { ItemID = 5, Name = "Maggi", Rating = 8 });
            _items.Add(new Item() { ItemID = 6, Name = "Quick Chow", Rating = 1 });
            _items.Add(new Item() { ItemID = 7, Name = "Maggi v2", Rating = 5 });


            _items.OrderByDescending(i => i.Rating)
                .Distinct(new DistinctByNameNearComparer<Item>())
                .Select(i => i)
                .ToList()
                .ForEach(i =>
                {
                    Console.WriteLine(i.Name);
                });

            Console.ReadKey();


            /* 
             * Expected result:
             * 
             * Jjamppong v2
             * Maggi
             * Quick Chow
             * 
             */
        }
    }

    class Item
    {
        public int ItemID { get; set; }
        public string Name { get; set; }
        public int Rating { get; set; }
    }

    class DistinctByNameNearComparer : IEqualityComparer<Item>
    {

        public bool Equals(Item x, Item y)
        {
            int _distance = LevenshteinDistance.Compute(x.Name, y.Name);
            int _maxLen = Math.Max(x.Name.Length, y.Name.Length);

            return (_distance > (_maxLen - 5));
        }

        public int GetHashCode(Item obj)
        {
            return obj.GetHashCode();
        }
    }

    class LevenshteinDistance
    {
        /// <summary>
        /// Compute the distance between two strings.
        /// </summary>
        public static int Compute(string s, string t)
        {
            int n = s.Length;
            int m = t.Length;
            int[,] d = new int[n + 1, m + 1];

            // Step 1
            if (n == 0)
            {
                return m;
            }

            if (m == 0)
            {
                return n;
            }

            // Step 2
            for (int i = 0; i <= n; d[i, 0] = i++)
            {
            }

            for (int j = 0; j <= m; d[0, j] = j++)
            {
            }

            // Step 3
            for (int i = 1; i <= n; i++)
            {
                //Step 4
                for (int j = 1; j <= m; j++)
                {
                    // Step 5
                    int cost = (t[j - 1] == s[i - 1]) ? 0 : 1;

                    // Step 6
                    d[i, j] = Math.Min(
                        Math.Min(d[i - 1, j] + 1, d[i, j - 1] + 1),
                        d[i - 1, j - 1] + cost);
                }
            }
            // Step 7
            return d[n, m];
        }
    }
}

i got an error here

_items.OrderByDescending(i => i.Rating)
                    .Distinct(new DistinctByNameNearComparer<Item>())
                    .Select(i => i)
                    .ToList()
                    .ForEach(i =>
                    {
                        Console.WriteLine(i.Name);
                    });

any help would be appreciated.

ANSWER:

class DistinctByNameNearComparer : IEqualityComparer<Item>
    {

        public bool Equals(Item x, Item y)
        {
            int _distance = LevenshteinDistance.Compute(x.Name, y.Name);
            int _maxLen = Math.Max(x.Name.Length, y.Name.Length);
            bool _comp = _distance < 4;

            return _comp;
        }

        public int GetHashCode(Item obj)
        {
            return 1;
        }
    }

Answer 1

I suppose you’re receiving Compiler Error CS0308, saying

The non-generic type-or-method ‘identifier’ cannot be used with type
arguments.

The method or type is not generic, but it was used with type
arguments. To avoid this error, remove the angled brackets and type
arguments, or redeclare the method or type as a generic method or
type.

So the correct linq would be:

_items.OrderByDescending(i => i.Rating)
    .Distinct(new DistinctByNameNearComparer())
    .Select(i => i)
    .ToList()
    .ForEach(i =>
    {
        Console.WriteLine(i.Name);
    });

while you specify

.Distinct(new DistinctByNameNearComparer<Item>())

The error is that DistinctByNameNearComparer is not generic, so you cannot specify a type parameter for it. Compiler infers from _items.OrderByDescending(i => i.Rating) that the argument for Distinct should be of type IEqualityComparer<Item> and you’re expected to specify it. However your DistinctByNameNearComparer is declared as

class DistinctByNameNearComparer : IEqualityComparer<Item>

that is, it really is IEqualityComparer<Item>. The only thing you need to do is to write

.Distinct(new DistinctByNameNearComparer())