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];
}

Answer 2

You could take a dictionary but make sure that you prevent duplicate key insertion. Keys of dictionary would serve as the unique numbers you need

Answer 3

You could toss them into a HashSet<int>. If you Add and it returns false, generate a new number.

Answer 4

Generate a list with your 37 items. Then in your for, select one and delete the selected

Answer 5

so I took your original code...found some logic errors and added the fix you were looking for to prevent random number duplicates.

Enjoy!

 System.Random generator = new Random(DateTime.Now.Millisecond);
            int[] lotteryNumber = new int[7];
            int lowerBounds = 1;
            int upperBounds = 8;
            int maxNumberLotteryValues = 7;

            if ( ( upperBounds - lowerBounds ) < (maxNumberLotteryValues))
            {
                Console.Write("Warning: Adjust your upper and lower bounds...there are not enough values to create a unique set of Lottery numbers! ");

            }
            else
            {
                Console.WriteLine("Your lottery numbers: ");
                for (int i = 0; i < maxNumberLotteryValues; i++)
                {
                    int nextNumber = generator.Next(lowerBounds, upperBounds);
                    int count = lowerBounds;  //Prevent infinite loop

                    while ((lotteryNumber.Contains(nextNumber))
                        && (count <= upperBounds))
                    {
                        nextNumber = generator.Next(lowerBounds, upperBounds);
                        count++;  //Prevent infinite loop
                    }

                    lotteryNumber[i] = nextNumber;
                    Console.Write("{0} ", lotteryNumber[i]);
                }
            }

            Console.ReadLine();

Answer 6

Maybe this could help, if you get the existing number just try to find new one that isn't in the array:

static void Main(string[] args)
        {
            System.Random generator = new Random(DateTime.Now.Millisecond); int[] lotteryNumber = new int[7];

            Console.WriteLine("Your lottery numbers: ");
            for (int i = 0; i < 7; i++)
            {
                int lNumber = 0;
                do
                {
                    lNumber = generator.Next(1, 37);
                }
                while (lotteryNumber.Contains(lNumber));
                lotteryNumber[i] = lNumber;

                Console.Write("{0} ", lotteryNumber[i]);
            }
            Console.ReadLine();
        }