Random number chosen except one

With Random.Range (0,10) a number between 0 and 10 is randomly chosen.
Now I want to have a random number between 0 and 10 except one specific number, for example 5.
So only from the numbers 0,1,2,3,4,6,7,8 and 9 one number is randomly chosen.

Does anybody know how to do that?

 

Code (csharp):

1. function RandomRangeExcept (min : int, max : int, except : int) : int {
2.     do {
3.         var number = Random.Range (min, max);
4.     } while (number == except);
5.     return number;
6. }

--Eric

 

Ok, thanks for quick reply.

 

Can you offer C# code,plz?

 

I'd like to offer an alternate solution:

Code (CSharp):

1. public int randomIntExcept( int min, int max, int except )
2. {
3.     int result = Random.Range( min, max-1 );
4.     if (result >= except) result += 1;
5.     return result;
6. }

Also keep in mind that Random.Range when given int values is max exclusive so Random.Range(0,10) will return a number in the range [0..9].


[EDIT] Here's a reference to Random.Range which goes into more detail about exclusive max for int and inclusive max for float: http://docs.unity3d.com/ScriptReference/Random.Range.html

 

Code (CSharp):

1. public int RandomExcept ( int fromNr, int exclusiveToNr, int exceptNr ) {
2.     int randomNr = exceptNr;
3.  
4.     while ( randomNr == exceptNr ) {
5.         randomNr = Random.Range( fromNr, exclusiveToNr );
6.     }
7.  
8.     return randomNr;
9. }

 

A slight variation to DarkArts Studios solution;

Code (CSharp):

1. public int RandomExcept(int min, int max, int except)
2. {
3.    int random = Random.Range(min, max);
4.    if (random >= except) random = (random + 1) % max;
5.    return random;
6. }
7.  

~
Another walk in the park.

 

I suggest avoiding while loops when possible. I'm not saying don't use while, just think before you use them. In two of the code samples above, if you set min == max == except, you will get an infinite loop.

Of course you can check and validate the input first, but I try to make it a habit to avoid possible infinite loops caused by while.

 

Agreed 100% with @Garth Smith (which is why I proposed the alternate solution above) - not only is there an infinite loop possibility but also, you have a small chance of a random fetch running for a relatively substantial amount of time especially if your min -> max difference is low.

And _always_ your time-till-return will be unpredictable. I don't like unpredictable code

 

I edit the answer of @toreau to make a function in C# where you can pass a List of exceptions.

Code (CSharp):

1. private int RandomExceptList(int fromNr, int exclusiveToNr, List<int> exceptNr)
2.     {
3.         //asigno el primer numero invalido
4.         int randomNr = exceptNr[0];
5.  
6.         // si el numero es invalido entra el en while
7.         while (exceptNr.Contains(randomNr))
8.         {
9.             randomNr = UnityEngine.Random.Range(fromNr, exclusiveToNr);
10.         }
11.  
12.         // cuando el numero sea valido... sale de la funcion
13.         return randomNr;
14.     }

I use it to fill an array of buttons with the wrong answers, the use my answer var to pick a random button an fill it with the correct answewer, hope it help you

here my code

Code (CSharp):

1. private void Update()
2.     {
3.             if (!buttonsSet)
4.             {
5.                 buttonsSet = true;
6.                 buttonsPanel.SetActive(true);
7.                 nextBtn.SetActive(false);
8.  
9.                 setWrongAnswers();
10.                 setCorrectAnswer();
11.             }
12.     }
13.  
14.     public void setWrongAnswers()
15.     {
16.         List<int> excludedNumbers = new List<int>();
17.         excludedNumbers.Add(answer);
18.         foreach (Text btnTxt in buttonsPanel.GetComponentsInChildren<Text>())
19.         {
20.             int anctaluNumber = RandomExceptList(0, 11, excludedNumbers);
21.             excludedNumbers.Add(anctaluNumber);
22.             btnTxt.text = anctaluNumber.ToString();
23.         }
24.     }
25.  
26.     public void setCorrectAnswer() {
27.         int randomBtn = UnityEngine.Random.Range(0, buttonsPanel.GetComponentsInChildren<Text>().Length);
28.         buttonsPanel.GetComponentsInChildren<Text>()[randomBtn].text = answer.ToString();
29.  
30.     }
31.  
32.     private int RandomExceptList(int fromNr, int exclusiveToNr, List<int> exceptNr)
33.     {
34.         int randomNr = exceptNr[0];
35.  
36.         while (exceptNr.Contains(randomNr))
37.         {
38.             randomNr = UnityEngine.Random.Range(fromNr, exclusiveToNr);
39.         }
40.         return randomNr;
41.     }

 

Here's solution with constant speed.

Code (CSharp):

1.  
2. private int RandomExcept(int min, int max, int except) {
3.    Debug.Assert(max > except, "max > except");
4.    Debug.Assert(except > min, "except > min");
5.    Debug.Assert(max < int.MaxValue, "max < int.MaxValue");
6.  
7.    if (Random.Range(0, 1 - float.Epsilon) > (except - min) / (float) (max - min)) {
8.       return Random.Range(min, except);
9.    }
10.  
11.    return 1 + Random.Range(except, max);
12. }
13.  

And if there are more than one excepts, I would first randomly weightened select interval, then just random number within interval.

 

I'm going to do a zombie and revive this thread.
We do not want a while loop for obvious performance reasons and because it could lead to an infinite loop.

In my solution, I generate a List that holds all allowed random numbers. Then I choose one of the allowed numbers in the array at random. This has decent performance and no while loop.

Code (CSharp):

1.  
2. public static int RandomRangeExcept(int minInclusive, int maxExclusive, List<int> except = null)
3.     {
4.         IEnumerable<int> allowedRandomNumbers = Enumerable.Range(minInclusive, maxExclusive - minInclusive);
5.         if (except != null)
6.         {
7.             allowedRandomNumbers = allowedRandomNumbers.Except(except);
8.         }
9.         if (allowedRandomNumbers.Count() == 0)
10.         {
11.             Debug.LogError("Allowed numbers array is empty! Returning 0");
12.             return 0;
13.         }
14.         int randomIndex = UnityEngine.Random.Range(0, allowedRandomNumbers.Count());
15.         return allowedRandomNumbers.ElementAt(randomIndex);
16.     }
17.  

 

Hey there, it's enough to randomize a number between

[min, max - 1]

. If the randomized number equals the exception number, we swap it with the value

(max - 1)

.
I take we want to randomize from

min (inclusive)

to

max (exclusive)

.

Code (CSharp):

1. private int GetRandomExcept(int min, int max, int exceptValue) // min (inclusive), max (exclusive)
2. {
3.     var r = Random.Range(min, max - 1);
4.     return r == exceptValue ? (max - 1) : r;
5. }