LevenshteinDistance.cs

/// <summary>
/// Number of changes needed to turn one string into another.
/// Taken from https://www.dotnetperls.com/levenshtein
/// </summary>
public static int LevenshteinDistanceTo(string s, string t)
{
  int n = s.Length;
  int m = t.Length;
  if (n == 0) return m;
  if (m == 0) return n;
  int[,] d = new int[n + 1, m + 1];

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

  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      int cost = (t[j - 1] == s[i - 1]) ? 0 : 1;
      d[i, j] = Math.Min(
        Math.Min(d[i - 1, j] + 1, d[i, j - 1] + 1),
        d[i - 1, j - 1] + cost);
    }
  }
  return d[n, m];
}

test.cs

using System;
using System.Collections.Generic;
					
public class Program
{
	public static void Main()
	{
		List<string[]> test = new List<string[]> {
			new string[]{"ant", "aunt"},
			new string[]{"Sam", "Samantha"},
			new string[]{"clozapine", "olanzapine"},
			new string[]{"flomax", "volmax"},
			new string[]{"toradol", "tramadol"},
			new string[]{"kitten", "sitting"}
		};
		foreach (string[] a in test) {
			int cost = Extensions.LevenshteinDistanceTo(a[0], a[1]);
			Console.WriteLine("{0} -> {1} = {2}", a[0], a[1], cost);
		}
	}
	// Output:
  // ant -> aunt = 1
  // Sam -> Samantha = 5
  // clozapine -> olanzapine = 3
  // flomax -> volmax = 3
  // toradol -> tramadol = 3
  // kitten -> sitting = 3
}