I'm new to C# and I'm making an application with arrays. I have an array with the numbers shown below:
int[] array2 = new int[] { 1, 3, 5, 7, 9 };
What I need to do is change the order of these numbers in the array without repetitions, because when I use Random Function, this shows me repeated numbers.
I saw this method, but do not know how to apply it with numbers: http://www.dotnetperls.com/shuffle
You can use the following LINQ chain:
int[] array2 = new int[] { 1, 3, 5, 7, 9 };
var random = new Random();
var total = (int)array2.
OrderBy(digit => random.Next()).
Select((digit, index) => digit*Math.Pow(10, index)).
Sum();
First, it orders the elements randomly, then it selects each element multiplied by 10 raised to the power of its index, then sums them together and casts the result to an integer. Also, please note that I didn't provide an useful seed for your Random instance. You might want to do that, to produce pseudo-random results.
You might also want to use a method for exponentiation described here, to avoid having to cast to an integer.
EDIT: As Rhumborl pointed out, you may just need the shuffled array. In that case:
var shuffledArray = array2.OrderBy(n => random.Next()).
ToArray();
Should work for you.
if you work in C# you better use C# structs.
You can use this generic function
using System;
using System.Collections.Generic;
public static class ListExtensions
{
public static void Shuffle<T>(this IList<T> list)
{
var randomNumber = new Random(DateTime.Now.Millisecond);
var n = list.Count;
while (n > 1)
{
n--;
var k = randomNumber.Next(n + 1);
var value = list[k];
list[k] = list[n];
list[n] = value;
}
}
}
and then your code should look like:
List<int> list2 = new List<int>(){1, 3, 5, 7, 9};
Shuffle(list2);
So as you said, you already have an array with numbers to work with. So I am not going to show you how to make an array filled with unique numbers.
This is how you shuffle your array.
Inside the loop do the following:
a. Generate a random number between 0 and idx1 (inclusive) using your method from Step 1. (Let the random number be idx2.)
b. Swap the elements in your array at idx1 and idx2.
A simple swap can be done by doing something like this:
int tmp = array[idx1];
array[idx1] = array[idx2];
array[idx2] = tmp;
The loop ends and you are left with a shuffled array.
I am not quite sure what you mean by changing the order without repetition. If you just want to generate a random number that never repeats you could do something like this
private Random rand = new Random();
private List<int> used = new List<int>;
protected int randomNonrepeating() {
int i = rand.next();
while(used.contains(i))
i = rand.next();
used.add(i);
return i;
}
My guess is, that is not quite what you are looking for though. If you just want to modify the algorithm at the supplied link to work with an array of integers as opposed to strings. You just need to change the types. Something like this
using System;
using System.Collections.Generic; using System.Linq;
static class RandomStringArrayTool { static Random _random = new Random();
public static string[] RandomizeStrings(int[] arr)
{
List<KeyValuePair<int, int>> list = new List<KeyValuePair<int, int>>();
// Add all strings from array
// Add new random int each time
foreach (var s in arr)
{
list.Add(new KeyValuePair<int, int>(_random.Next(), s));
}
// Sort the list by the random number
var sorted = from item in list
orderby item.Key
select item;
// Allocate new string array
int[] result = new string[arr.Length];
// Copy values to array
int index = 0;
foreach (KeyValuePair<int, int> pair in sorted)
{
result[index] = pair.Value;
index++;
}
// Return copied array
return result;
}
}
Hope this helps.
