Shillelagh Posts - Answer Overflow

Shillelagh

•Created by Shillelagh on 8/1/2023 in #help

❔ Create new instance of type unknown at runtime?

Say I have a base class, abstract class Letter with child classes A, B, and C. If I have a variable: Letter myLetter which is of unknown type (can be any of A, B, or C, the only guarantee is it's a child of Letter), how can I create a new instance of whatever class myLetter is? I need to create a new instance (must call default constructor as well) of whatever myLetter is and store it in another variable (say myLetter2)

34 replies

CC#

•Created by Shillelagh on 7/30/2023 in #help

❔ Troubles getting all Largest Common Subsequences of two strings.

For fun trying to write a system to take differential backups of strings. The backbone is this method I wrote, which should find all LCSs between two strings:

        public static List<Tuple<int, int, int>> GetAllLCS(string _new, string _old)
        {
            List<Tuple<int, int, int>> _matches = new List<Tuple<int, int, int>>(); // Get all common substrings
            for (int i = 0; i < _new.Length; i++)
            {
                for (int j = _new.Length; j > i; j--)
                {
                    var o = _old.IndexOf(_new.Substring(i, j - i));
                    if (o != -1)
                    {
                        _matches.Add(Tuple.Create(i, j, o));
                    }
                }
            }

            _matches.Sort(new Comparison<Tuple<int,int,int>>((x, y) => { // Sort them from largest to smallest substrings
                return (x.Item2 - x.Item1)-(y.Item2 - y.Item1);
            }));
            var _outmatches = new List<Tuple<int, int, int>>();

            foreach (var i in _matches) // Duplicate the list
            {
                _outmatches.Add(i);
            }

            foreach (var i in _matches) // Remove any substrings that overlap
            {
                foreach (var j in _matches)
                {
                    if (i == j) continue;
                    if ((j.Item1 > i.Item1 && j.Item1 < i.Item2 - 1) || (j.Item2 > i.Item1 && j.Item2 < i.Item2 - 1)) _outmatches.Remove(j);
                }
            }

            return _outmatches;
        }

        public static List<Tuple<int, int, int>> GetAllLCS(string _new, string _old)
        {
            List<Tuple<int, int, int>> _matches = new List<Tuple<int, int, int>>(); // Get all common substrings
            for (int i = 0; i < _new.Length; i++)
            {
                for (int j = _new.Length; j > i; j--)
                {
                    var o = _old.IndexOf(_new.Substring(i, j - i));
                    if (o != -1)
                    {
                        _matches.Add(Tuple.Create(i, j, o));
                    }
                }
            }

            _matches.Sort(new Comparison<Tuple<int,int,int>>((x, y) => { // Sort them from largest to smallest substrings
                return (x.Item2 - x.Item1)-(y.Item2 - y.Item1);
            }));
            var _outmatches = new List<Tuple<int, int, int>>();

            foreach (var i in _matches) // Duplicate the list
            {
                _outmatches.Add(i);
            }

            foreach (var i in _matches) // Remove any substrings that overlap
            {
                foreach (var j in _matches)
                {
                    if (i == j) continue;
                    if ((j.Item1 > i.Item1 && j.Item1 < i.Item2 - 1) || (j.Item2 > i.Item1 && j.Item2 < i.Item2 - 1)) _outmatches.Remove(j);
                }
            }

            return _outmatches;
        }

21 replies

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