im trying to create a lottery ticket generator where i have 5 numbers (from 1 to 50) and 2 other numbers (from 1 to 12) called stars. The five numbers cant be the same and the 2 stars cant be the same too (but can be equal to the numbers). I have to make the code in c# and put in a cshtml page with a ViewBag. My output somehow is giving me this: Output

My c# code is:

Random random = new Random();
            int number = random.Next();
                int[] numbers = new int[5];
            int[] stars = new int[2];
            bool repeated = false;
            int newnumber = 0;

            for (int i = 0; i < 5; i  )
            {
                repeated = false;
                while (repeated == true)
                {
                    newnumber = random.Next(1, 50);
                    repeated = numbers.Contains(newnumber);
                }

                numbers[i] = newnumber;

            }
            ViewBag.numbers = numbers;

            for (int i = 0; i < 2; i  )
            {
                repeated = false;
                while (repeated == true)
                {
                    newnumber = random.Next(1, 12);
                    repeated = stars.Contains(newnumber);
                }
                stars[i] = newnumber;
            }
            ViewBag.stars = stars;

         
            return View("MyView");

Then i put this in cshtml so it appear in my website:

<div  style="width: 400px; height: 125px; margin: auto">
            <div >
                <h3 style="text-align:center">Lottery</h3>
                <p style="text-align:center">Winning numbers!</p>
               
                <p style="text-align:center">
                    Nº:@for (int i=0; i <5;i  )
                {
                    @Html.Raw(ViewBag.numbers[i] ";")
                }
                |
                    <i ></i>:@for (int i=0; i <2;i  )
                {
                    @Html.Raw(ViewBag.stars[i] ";")
                }
                </p>           
                </div>
        </div>

Can you guys help me? I really dont know where is the mistake that makes the lottery ticket have just zeros.

Thank you.

CodePudding user response：

Here:

repeated = false;
while (repeated == true)

It will always skip while.

CodePudding user response：

You assign repeated == false so it would never go into the while loop. Change the code to do while it should work for you.

 do
                {
                     //Create random number
                     //Check whether it's repeated
                     newnumber = random.Next(1, 12);
                     repeated = stars.Contains(newnumber);
                }while (repeated == true);

CodePudding user response：

Regenerating numbers if there are repetitions is not very efficient. Try this:

var random = new Random();
var allNumbers = Enumerable.Range(1, 50);
var stars = allNumbers
    .OrderBy(x => random.Next())
    .Take(2)
    .ToArray();
var numbers = allNumbers
    .Except(stars)
    .OrderBy(x => random.Next())
    .Take(5);

CodePudding user response：

There are two typical methods to create unique random k numbers from n:

1. Create all n numbers, shuffle and then take k of them (this method is efficient when k ~ n):

// Simplest, Fisher-Yates algorithm is faster
// https://en.wikipedia.org/wiki/Fisher–Yates_shuffle
int[] numbers = Enumerable
  .Range(1, n)
  .OrderBy(item => random.NextDouble())
  .Take(k)
  .ToArray();

2. Generare k random numbers while testing for being unique (do it when k << n):

HashSet<int> data = new HashSet<int>();

while (data.Count < k)
  data.Add(random.Next(1, n   1));

numbers = data.ToArray();

In your case we can extract the method:

private static Random s_Random = new Random();

private static int[] Generate(int count, int total) => Enumerable
  .Range(1, total)
  .OrderBy(_ => s_Random.NextDouble())
  .Take(count)
  .ToArray();

Then you can just call the routine:

ViewBag.numbers = Generate(5, 50);
ViewBag.stars = Generate(2, 12);