ShuffleBag.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

// a different way of generating random values that may "feel" better than true randomness
// every possible value will show up once, but in a random order
// it simply draws from the "bag" every time you get NextValue
// 
// construct either with a list of values, or a size for the most common use
// list values like: new {1, 1, 2, 2, 3, 4};
// size constructor makes a list of numbers from 0 to size-1

// incidentally, you may want to call Random.InitState(seed) outside this object
// in order to get the same "random" sequence each playthrough

public class ShuffleBag {
	private int currentPosition;
	private int[] numberList;

	public int NextValue {
		get {
			int val = numberList[currentPosition];
			currentPosition++;
			if (currentPosition >= numberList.Length) {
				Reset();
			}
			return val;
		}
	}

	public ShuffleBag(int[] numbers) {
		numberList = ShuffleArray(numbers);
	}
	public ShuffleBag(int listSize) {
		numberList = new int[listSize];
		for (int i = 0; i < listSize; ++i) {
			numberList[i] = i;
		}
		numberList = ShuffleArray(numberList);
	}

	private void Reset() {
		int lastValue = numberList[numberList.Length-1];
		numberList = ShuffleArray(numberList);

		// make sure not to repeat last value
		if (numberList[0] == lastValue) {
			int r = Random.Range(1, numberList.Length);
			numberList[0] = numberList[r];
			numberList[r] = lastValue;
		}

		currentPosition = 0;
	}

	// implementation of Knuth shuffle algorithm
	public static int[] ShuffleArray(int[] numbers) {
		int[] newArray = numbers.Clone() as int[];

		for (int i = 0; i < newArray.Length; ++i) {
			int tmp = newArray[i];
			int r = Random.Range(i, newArray.Length);
			newArray[i] = newArray[r];
			newArray[r] = tmp;
		}

		return newArray;
	}
}