2 replies to this topic

[TomTheBeast]

Hey, well I'm wondering how I could use Random to recieve a random numer of a list and make sure it isnt used.
For example, I have a list called NumsToUse, which contains all digits from 0 to 9. I have to take the digits from that, and randomly place them in a string without there being any repeats. I'm not sure how i would do this, but my strcutre of it would be something like:

public List<int> NumsToUse = new List<int>();
public string getNums() {
string thestoof;
Random rnd = new Random();
int next = rnd.Next(0,9);
if (NumsToUse.Contains(next)) {
thestoof = (thestoof + ", " + next);
NumsToUse.Remove(next);
}
return thestoof;
}

But then how would I make it so when it checks if it contains the number, that isnt being used, to when it IS being used to redo the check?

I've figured out how i could do this, via recurison, and I've tried this method and now i get a Stack Overflow Exeception:

public int ifNum()
		{
				int next = num.Next(0, 9);
				if (!(Nums.Contains(next)))
				{
					Nums.Add(next);
					return next;
				}
				return ifNum();
		}

		public void Randomize()
		{
			foreach (Control button in panel1.Controls)
			{
				if (button.GetType() == typeof(Button))
				{
					int newNum = ifNum();
					button.Text = newNum.ToString();
				}
			}
		}

[kernelcoder]

You can use the following method to do your job. The method GetUniqeNumbers returns a string of length 10 which contains all the numbers 0-9 exactly once and the numbers will be random.

public static String GetUniqeNumbers()
{
	String numbers = String.Empty;
	Random rnd = new Random(5);
	while (numbers.Length < 9) {
		int number = rnd.Next(0, 9);
		if (!numbers.Contains(number.ToString())) {
			numbers += number.ToString();
		}
	}

	for (int number = 0; number <= 9; number++) {
		if (!numbers.Contains(number.ToString())) {
			numbers += number.ToString();
			break;
		}
	}

	return numbers;
}

[Momerath]

You'd want to use a Fisher-Yates (Knuth) Shuffle. No expensive Contains searches each round, no hoping that the next random number isn't already used. Runs in linear time.