Avoiding random duplicates

Question

System.Random generator = new Random(DateTime.Now.Millisecond);
int[] lotteryNumber = new int[7];

Console.WriteLine(\"Your lottery numbers: \");
for (int i = 0; i&l         


        

Answer 1

If you're trying to pick numbers from a range without repetitions, you need to create an array of all the possible numbers and then "shuffle" a random selection out:

int[] allPossibleNumbers = Enumerable.Range(1, 37).ToArray();
int[] lotteryNumber = new int[7];
for (int i = 0; i < 7; i++)
{
    int index = r.Next(i, 37);
    lotteryNumber[i] = allPossibleNumbers[index];
    allPossibleNumbers[index] = allPossibleNumbers[i];
    // This step not necessary, but allows you to reuse allPossibleNumbers
    // rather than generating a fresh one every time.
    // allPossibleNumbers[i] = lotteryNumber[i];
}