How to Generate random numbers without the same number

Question

Can you please give me the answer how can i generate numbers without the same numbers ? Because i am creating a lottery program, and i want my program having no same numbers because the lottery is not having an output that has the same numbers.

Why do you say that, that the lottery does not have the same numbers. Do you mean not the same number in a set of numbers? — Hogan, Dec 11 '13 at 19:26
possible duplicate of [how do i seed a random class to avoid getting duplicate random values](http://stackoverflow.com/questions/1785744/how-do-i-seed-a-random-class-to-avoid-getting-duplicate-random-values) — John, Dec 11 '13 at 19:27
@Hogan Surely you know how lotteries work. Combination of `k` number out of `n` without replacement. — millimoose, Dec 11 '13 at 19:27
@Hogan When you have a lottery you're selecting, say, 5 numbers between 1 and 100, but those 5 numbers should be unique. The lottery is never 1,1,1,1,1. — Servy, Dec 11 '13 at 19:27
Yes guys, I answered that question, I'm still not sure it was what was being asked, but I answered what the question seemed to be asking. — Hogan, Dec 11 '13 at 19:28
possible duplicate of [Select a random N elements from List in C#](http://stackoverflow.com/questions/48087/select-a-random-n-elements-from-listt-in-c-sharp) — Alexei Levenkov, Dec 11 '13 at 20:06

score 1 · Answer 1 · answered Dec 11 '13 at 19:27

1

I believe what you want to do is use the Set specialized collection. Pick a random item left in the Set and then remove it from the set. Pick another.

answered Dec 11 '13 at 19:27

Hogan

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score 0 · Answer 2 · answered Dec 11 '13 at 19:31

0

Be careful with multithreading and random initialization.

static Random r = new Random();
static IEnumerable<int> Randoms(int max)
{
    while(true)
        yield return r.Next(max);
}

Usage:

var items = Randoms(50).Distinct().Take(10).ToArray();

answered Dec 11 '13 at 19:31

Oleh Nechytailo

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score 0 · Answer 3 · answered Dec 11 '13 at 19:55

You now you need to put it in a recursive method, but here is a simple way.

using System;
using System.Collections.Generic;
using System.Linq;

public class Test
{
    public static void Main()
    {
        List<int> numbers = new List<int>();
        numbers.Add(1);
        numbers.Add(2);
        numbers.Add(3);
        numbers.Add(4);
        numbers.Add(5);
        numbers.Add(6);
        numbers.Add(7);

        Random rand = new Random();

        var numbersSfle = numbers.OrderBy(item => rand.Next()).ToList();
        Console.Write(numbersSfle[0].ToString());
        numbers.RemoveAt(0);


        numbersSfle = numbers.OrderBy(item => rand.Next()).ToList();
        Console.Write(numbersSfle[0].ToString());
        numbers.RemoveAt(0);
    }
}

The fiddle:

http://ideone.com/p39Lhg

How to Generate random numbers without the same number

3 Answers3