for-loop dynamic/recursive?

Question

I have the problem that I've got 6 for-loops but I want to remove the loops and replace them with a recursive/dynamic method.. sadly I dont have a clue how I can do this. Maybe one of you can help me.

for (int a = 1; a < 45; a++)
                {
                    for (int b = a + 1; b < 46; b++)
                    {
                        for (int c = b + 1; c < 47; c++)
                        {
                            for (int d = c + 1; d < 48; d++)
                            {
                                for (int e = d + 1; e < 49; e++)
                                {
                                    for (int f = e + 1; f < 50; f++)
                                    {                                           
                                        counter++;
                                        new_counter = zaehler.ToString("N0");
                                        Console.WriteLine(a + " " + b + " " + c + " " + d + " " + e + " " + f + " | -> " + new_counter);
                                        if (zaehler == 13983816)
                                        {
                                            Console.ForegroundColor = ConsoleColor.Green;
                                            Console.WriteLine($"{new_counter} combinations.");
                                            Console.ReadKey();
                                        }
                                    }
                                }
                            }
                        }
                    }
                }

This feels like a XY Problem - meta.stackexchange.com/questions/66377/what-is-the-xy-problem . Talk us through what the code should be doing. — mjwills
– mjwills, Commented Feb 7, 2019 at 10:09
What´s your actual problem? your code is pretty straight-forward to me. You could of course introduce some method, however I can´t see any reason to introduce some recursion here. — MakePeaceGreatAgain
– MakePeaceGreatAgain, Commented Feb 7, 2019 at 10:09
What do you mean by "dynamic" here? Also, what would recursion do for you other than maybe make things a bit slower and risk an overflow? — Jon Hanna
– Jon Hanna, Commented Feb 7, 2019 at 10:09
by "dynamic" here, do you mean "more flexible depth", so: not hard coded to 6? — Marc Gravell
– Marc Gravell, Commented Feb 7, 2019 at 10:15
@HimBromBeere I would like to have it more dynamic so when I want to change the values I dont have to change the code. In my opinion there would be a dynamic method better — darby
– darby, Commented Feb 7, 2019 at 10:16

Marc Gravell · Accepted Answer · 2019-02-07 10:25:49Z

3

The overall intent here is a little hard to grok, but here is a dynamically recursive version that seems to do something similar; I haven't fully checked it for equivalence:

static void RunLoop(int depth, int from, int to, Action<int, int[]> callback)
{
    int[] tokens = new int[depth];
    int counter = 0;
    RunLoop(tokens, 0, from, to, callback, ref counter);
}
private static void RunLoop(int[] tokens, int index, int from, int to,
    Action<int, int[]> callback, ref int counter)
{
    int nextIndex = index + 1;
    for(int i = from; i < to; i++)
    {
        tokens[index] = i;
        if (nextIndex == tokens.Length)
        {
            callback(counter, tokens);
            counter++; // post-increment when invoking the callback
        }
        else
        {
            counter++; // pre-increment when diving
            RunLoop(tokens, nextIndex, i + 1, to + 1, callback, ref counter);
        }
    }
}

with usage:

public static void Main()
{
    RunLoop(6, 1, 45, (i, arr) => Console.WriteLine(i + ": " + string.Join(", ", arr)));
}

Your "what to do when reaching the innermost depth" goes in callback; the first argument is the overall counter so far, and the second argument is the successive tokens that make up that value.

answered Feb 7, 2019 at 10:25

Marc Gravell

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2 Comments

darby Over a year ago

Holy! I thank you so much! This had me left some sleepless nights.. holy shit you have paypal or anything where I can send you something??

Marc Gravell Over a year ago

@darby I have a buymeacoffee, but you really don't need to do that; I do this stuff for fun!

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