Create duplicate items and submit them inside a list

Question

Hello let me show you the problem with very simple explanation.

I have this;

int[] numbers1= { 1, 2, 3 };

and i need this;

int[] numbers2= { 1,1,1, 2,2,2, 3,3,3 };

how can i duplicate my values then use them in another list?

Lets have a look at this without starting to write code. This is very plain logic and it seems you dont have the steps already planed and figured out. We need to take the values from numbers1, iterate each value x times and save them in the array numbers2. What steps do you need for that? What values will be important? — Cataklysim, Apr 22 '22 at 09:20

score 7 · Accepted Answer · answered Apr 22 '22 at 09:19

Try:

using System.Linq;

namespace WebJob1
{
    internal class Program
    {

        static void Main()
        {
            int[] numbers1 = { 1, 2, 3 };
            var numbers2 = numbers1.SelectMany(x => Enumerable.Repeat(x,3)).ToArray();
        }
    }
}

score 2 · Answer 2 · answered Apr 22 '22 at 09:21

2

You can try this:

    int multiplier = 3;
    int[] numbers1 = { 1, 2, 3 };

    var numbers2 = numbers1.SelectMany(x => Enumerable.Repeat(x, multiplier)).ToArray();

Maybe some useful information about LINQ extentions Select and SelectMany here.

answered Apr 22 '22 at 09:21

Dominik

300
1
14

score 2 · Answer 3 · answered Apr 22 '22 at 09:21

2

You can do this with LINQ

var numbers2 = numbers1.SelectMany(x => new[]{x,x,x});

Live example: https://dotnetfiddle.net/FLAQIY

answered Apr 22 '22 at 09:21

Jamiec

133,658
13
134
193

but what about if you don't know the quantity? – Leandro Bardelli Apr 01 '23 at 16:28
@LeandroBardelli If you look at one of the other answers by Dominik it's basically the same but with a variable for how many repeats you want. – Jamiec Apr 03 '23 at 07:57
Yes saw it late sorry – Leandro Bardelli Apr 03 '23 at 14:11

score 0 · Answer 4 · answered Aug 30 '22 at 21:54

What about an algoritmic answer:

public class Program
{
    public static void Main()
    {
        int[] numbers1= { 1, 2, 3 };
        var numbers2 = ArrayMultiplier.MultiplyArray(numbers1, 3);  //{ 1,1,1,2,2,2,3,3,3 }
    }
    
    public static class ArrayMultiplier{
        public static int[] MultiplyArray(int[] array, int multiplicationCount){
            int[] result = new int[array.Length*multiplicationCount];
            for(int i =0; i<array.Length; i++){
                for(int j = 0; j<multiplicationCount; j++){
                    result[i*multiplicationCount + j] = array[i];
                }
            }
            return result;
        }
    }   
}

Create duplicate items and submit them inside a list

4 Answers4