Computes edit distance recursively between to string in C#.

EditDistanceRecursive.cs

public static int EditDistanceRecursive(string str1, string str2, int m, int n) 
{
    if(m < 0 || n < 0 ||
       m >= str1.Length ||
       n >= str2.Length)
    {
        throw new ArgumentOutOfRangeException();
    }
    
    if(m == 0 && n == 0)
    {
        return 0;
    }
    if(m == 0)
    {
        return n;
    }
    if(n == 0)
    {
        return m;
    }

    int left = EditDistanceRecursive(str1, str2, m-1, n) + 1;
    int right = EditDistanceRecursive(str1, str2, m, n - 1) + 1;
    int middle = EditDistanceRecursive(str1, str2, m - 1, n - 1) + ((str1[m] == str2[n]) ? 0 : 1);

    return Min(Min(left, right), middle);
}