ShuffleAndPick.cs

using UnityEngine;

// @kurtdekker
//
// ultra-simple core of "shuffle and pick"
//
// drop this on a blank GameObject and run

public class ShuffleAndPick : MonoBehaviour
{
	void PerformShuffleAndPick()
	{
		// however you want to initialize this, have
		// ONE copy of each thing in it:

		// source data
		int[] things = new int[] { 1, 3, 4, 10, 22, 33, 199, 2000, };

		// shuffle
		for (int i = 0; i < things.Length; i++)
		{
			int j = Random.Range(i, things.Length);

			var t = things[i];
			things[i] = things[j];
			things[j] = t;
		}

		// how much do we want?
		int count = 3;

		// safety
		if (count > things.Length)
		{
			Debug.LogWarning("You want " + count + " items but I only have " + things.Length);
			count = things.Length;
		}

		// somewhere to store the final output
		int[] finalResult = new int[count];

		// pick
		for (int i = 0; i < count; i++)
		{
			var thing = things[i];

			finalResult[i] = thing;
		}

		// ONLY do this if you need them in ascending order:
		System.Array.Sort(finalResult);

		// announce
		Debug.Log("I choose these " + count + " things:");

		// display items
		for (int i = 0; i < finalResult.Length; i++)
		{
			int result = finalResult[i];

			Debug.Log(result.ToString());
		}
	}

	private void Start()
	{
		PerformShuffleAndPick();
	}
}