How to check there is the same Random object

Question

I'm doing simple Xamarin.Forms puzzle game and i need to have 9 puzzles with diffrent random values. I tried to check it with some loops, but it's still not working.

Random r = new Random();

            Label[] puzzles = { puz1, puz2, puz3, puz4, puz5, puz6, puz7, puz8, puz9 };
            string[] used = new string[9];
            for (int i = 0; i < puzzles.Length; i++)
            {
                if (i > 0)
                {
                    for (int x = 1; x < used.Length; x++)
                    {
                        do
                        {
                            puzzles[i].Text = Puzzles.puz[r.Next(0, 8)];
                            used[x] = puzzles[i].Text;
                        }
                        while (used[x - 1] == used[x]);
                    }
                }
                else
                {
                    puzzles[i].Text = Puzzles.puz[r.Next(0, 8)];
                    used[0] = puzzles[i].Text;
                }
            }

And Puzzles.cs class

class Puzzles
    {
        public static string[] puz = { "1", "2", "3", "4", "5", "6", "7", "8", "9" };


    }

How can I check that new generated puzzle hasn't the same value that puzzles generated previously?

Can you elaborate on how your code "doesn't work"? What were you expecting, and what actually happened? If you got an exception/error, post the line it occurred on and the exception/error details as per the How to Create a [mcve] page. Please [edit] your question to add these details into it or we may not be able to help. — gunr2171, Mar 28 '19 at 18:06
Possible duplicate of [Easiest way to compare arrays in C#](https://stackoverflow.com/questions/3232744/easiest-way-to-compare-arrays-in-c-sharp) — NineBerry, Mar 28 '19 at 18:06
Are you trying to shuffle an array? This is a really bad way to shuffle an array. Implement a Knuth shuffle; there are hundreds of examples on this site or the internet at large. — Eric Lippert, Mar 28 '19 at 18:07
"Checking for duplicate random values" almost always means you should really be using a shuffle: take N values and put them in random order. — Ňɏssa Pøngjǣrdenlarp, Mar 28 '19 at 18:17

Olivier Samson · Accepted Answer · 2019-03-29T03:12:55.383

This is because you only check the preceding value for duplicates, making it still possible for used[x -2] == used[x] to be true.

To achieve your goal, I would suggest implementing a shuffle function, like the one you can find here. It can give something like this

// Implemented somewhere in your code
private List<E> ShuffleList<E>(List<E> inputList)
{
     List<E> randomList = new List<E>();

     Random r = new Random();
     int randomIndex = 0;
     while (inputList.Count > 0)
     {
          randomIndex = r.Next(0, inputList.Count); //Choose a random object in the list
          randomList.Add(inputList[randomIndex]); //add it to the new, random list
          inputList.RemoveAt(randomIndex); //remove to avoid duplicates
     }

     return randomList; //return the new random list
}

// Then for each element of your puzzles array, you could do
puzzles[i].Text = SuffleList(Puzzles.puz);

Oh lol, I will try to correct it... I guess my brain went wrong lol — Olivier Samson, Mar 29 '19 at 02:46

score 0 · Answer 2 · answered Mar 28 '19 at 22:04

Thanks all for help, I didn't know Shuffle mechanism. Finally my 'working' code presents as follows

        static Random rnd = new Random();

        static void Shuffle<T>(T[] array)
        {
            int n = array.Length;
            for (int i = 0; i < n; i++)
            {
                int r = i + rnd.Next(n - i);
                T t = array[r];
                array[r] = array[i];
                array[i] = t;
            }
        }

        public Game()
        {
            InitializeComponent();


            Label[] puzzles = { puz1, puz2, puz3, puz4, puz5, puz6, puz7, puz8, puz9 };

            string[] puz = { "1", "2", "3", "4", "5", "6", "7", "8" };

            Shuffle(puz);
            for (int i = 0; i < puzzles.Length - 1; i++)
            {
                puzzles[i].Text = puz[i];
            }
        }

How to check there is the same Random object

2 Answers2