C# How to randomize the number on 10 buttons (0 - 9) without duplicates

Question

1.This is what i've got this so far

2.Its suppposed to randomize the numbers on the buttons when it starts. But it still generates duplicates (and i dont want duplicates).

I use Visual studio 2012 C# for this

Its only supposed to do it once i startup the program. So its a one time randomize

            Random rand = new Random();
            int RandomOne = rand.Next(0, 10);
            int RandomTwo = rand.Next(0, 10);
            int RandomThree = rand.Next(0, 10);
            int RandomFour = rand.Next(0, 10);
            int RandomFive = rand.Next(0, 10);
            int RandomSix = rand.Next(0, 10);
            int RandomSeven = rand.Next(0, 10);
            int RandomEight = rand.Next(0, 10);
            int RandomNine = rand.Next(0, 10);
            int RandomZero = rand.Next(0, 10);

            btnOneNgra.Text = Convert.ToString(RandomOne);


            if ((RandomTwo == RandomOne) || (RandomTwo == RandomNine) || (RandomTwo == RandomThree) || (RandomTwo == RandomFour)
                || (RandomTwo == RandomFive) || (RandomTwo == RandomSix) || (RandomTwo == RandomSeven) || (RandomTwo == RandomEight) || (RandomTwo == RandomZero))
            {
                RandomTwo = rand.Next(0, 10);
            }
            else 
            {
                btnTwoNgra.Text = Convert.ToString(RandomTwo);
            }


            if ((RandomThree == RandomOne) || (RandomThree == RandomTwo) || (RandomThree == RandomNine) || (RandomThree == RandomFour)
                || (RandomThree == RandomFive) || (RandomThree == RandomSix) || (RandomThree == RandomSeven) || (RandomThree == RandomEight) || (RandomThree == RandomZero))
            {
                RandomThree = rand.Next(0, 10);
            }
            else
            {
                btnThreeNgra.Text = Convert.ToString(RandomThree);
            }


            if ((RandomFour == RandomOne) || (RandomFour == RandomTwo) || (RandomFour == RandomThree) || (RandomFour == RandomNine)
                || (RandomFour == RandomFive) || (RandomFour == RandomSix) || (RandomFour == RandomSeven) || (RandomFour == RandomEight) || (RandomFour == RandomZero))
            {
                RandomFour = rand.Next(0, 10);
            }
            else
            {
                btnFourNgra.Text = Convert.ToString(RandomFour);
            }


            if ((RandomFive == RandomOne) || (RandomFive == RandomTwo) || (RandomFive == RandomThree) || (RandomFive == RandomFour)
                || (RandomFive == RandomNine) || (RandomFive == RandomSix) || (RandomFive == RandomSeven) || (RandomFive == RandomEight) || (RandomFive == RandomZero))
            {
                RandomFive = rand.Next(0, 10);
            }
            else
            {
                btnFiveNgra.Text = Convert.ToString(RandomFive);
            }


            if ((RandomSix == RandomOne) || (RandomSix == RandomTwo) || (RandomSix == RandomThree) || (RandomSix == RandomFour)
                || (RandomSix == RandomFive) || (RandomSix == RandomNine) || (RandomSix == RandomSeven) || (RandomSix == RandomEight) || (RandomSix == RandomZero))
            {
                RandomSix = rand.Next(0, 10);
            }
            else
            {
                btnSixNgra.Text = Convert.ToString(RandomSix);
            }


            if ((RandomSeven == RandomOne) || (RandomSeven == RandomTwo) || (RandomSeven == RandomThree) || (RandomSeven == RandomFour)
                || (RandomSeven == RandomFive) || (RandomSeven == RandomSix) || (RandomSeven == RandomNine) || (RandomSeven == RandomEight) || (RandomSeven == RandomZero))
            {
                RandomSeven = rand.Next(0, 10);
            }
            else
            {
                btnSevenNgra.Text = Convert.ToString(RandomSeven);
            }


            if ((RandomEight == RandomOne) || (RandomEight == RandomTwo) || (RandomEight == RandomThree) || (RandomEight == RandomFour)
                || (RandomEight == RandomFive) || (RandomEight == RandomSix) || (RandomEight == RandomSeven) || (RandomEight == RandomNine) || (RandomEight == RandomZero))
            {
                RandomEight = rand.Next(0, 10);
            }
            else
            {
                btnEightNgra.Text = Convert.ToString(RandomEight);
            }


            if ((RandomNine == RandomOne) || (RandomNine == RandomTwo) || (RandomNine == RandomThree) || (RandomNine == RandomFour)
                || (RandomNine == RandomFive) || (RandomNine == RandomSix) || (RandomNine == RandomSeven) || (RandomNine == RandomEight) || (RandomNine == RandomZero))
            {
                RandomNine = rand.Next(0, 10);
            }
            else 
            {
                btnNineNgra.Text = Convert.ToString(RandomNine);
            }


            if ((RandomZero == RandomOne) || (RandomZero == RandomTwo) || (RandomZero == RandomThree) || (RandomZero == RandomFour)
                || (RandomZero == RandomFive) || (RandomZero == RandomSix) || (RandomZero == RandomSeven) || (RandomZero == RandomEight) || (RandomZero == RandomNine))
            {
                RandomZero = rand.Next(0, 10);
            }
            else
            {
                btnZeroNgra.Text = Convert.ToString(RandomZero);
            }

One solution could be to add the numbers(0-9) to a list, shuffle and select a random index, remove element at the index. repeat. EDIT: perhaps select the next index - not a random index after the shuffle. — Faheem, May 10 '17 at 12:07
You need to do this in a while loop and not a single if-statement. If you check it once and then change it, it may get the same value like another also has. — Daniel Frühauf, May 10 '17 at 12:07
Can you give me an example code of how im supposed to do so. Im still a student and need to learn — Noah De Graaff, May 10 '17 at 12:11
@NoahDeGraaff If you need to learn I suggest you go try it out. Copy code from SO doesn't teach you anything. — DavidG, May 10 '17 at 12:17

Ian · Answer 1 · 2017-05-10T12:14:00.513

0

The approach for this case should be to create ten numbers in a list and then take one by one to avoid duplication, something like the following:

List<int> nums = new List<int>(Enumerable.Range(0, 10));

private int getNumber(){
    Random rand = new Random();
    int index = rand.Next(0, nums.Count);
    int num = nums[index];
    nums.RemoveAt(index);
    return num;
}

You might need to be careful though, it cannot be called more than 10 times... You might want to create little error handler like:

private int getNumber(){
    if(nums.Count >= 0)
        return -1; //means not available
    Random rand = new Random();
    int index = rand.Next(0, nums.Count);
    int num = nums[index];
    nums.RemoveAt(index);
    return num;
}

edited May 10 '17 at 12:14

answered May 10 '17 at 12:09

Ian

30,182
19
69
107

1

I recommend using `Enumerable.Range(0, 9)` to generate the list of numbers. That way you can make it dynamic. – DavidG May 10 '17 at 12:13
@DavidG good idea... since the second element is `count` I think I should go with `0,10` though – Ian May 10 '17 at 12:14
I think `.ToList()` looks better, but this works too :) – DavidG May 10 '17 at 12:15

score -1 · Answer 2 · answered May 10 '17 at 12:56

-1

Maybe you should try with HashSet:

HashSet<int> numbers = new HashSet<int>();
Random randomizer = new Random();

while (numbers.Count < 10)
{
   numbers.Add(randomizer.Next(0, 10));
}

HashSet would make sure that all the values are unique.

answered May 10 '17 at 12:56

gvozdeni88

9
1

It would also throw an exception and not give you all the numbers from 0-9 without running it potentially for a very long time (from a probabilistic standpoint) – DavidG May 10 '17 at 12:59
It does not throw an exception – gvozdeni88 May 10 '17 at 13:00
OK, yes it won't throw an exception but the loop will run dozens of unnecessary times. – DavidG May 10 '17 at 13:02
For info, I have tested this a few times. Sometimes it takes less than 20 loops, sometimes it takes over 100. – DavidG May 10 '17 at 13:04

C# How to randomize the number on 10 buttons (0 - 9) without duplicates

2 Answers2