import java.util.Random;

public class ArrayFiller {

	long seed;
	int sparsity;
	private boolean covering;

	/**
	 * @param seed
	 *            the seed for the random number generator
	 * @param sparsity
	 *            the average interval between successive values in the array (hopefully)
	 * @param covering
	 *            whether the M array should be made to cover the range of possible values of sums of pairs of elements in the L array
	 */
	public ArrayFiller(long seed, int sparsity, boolean covering) {
		super();
		this.seed = seed;
		this.sparsity = sparsity;
		this.covering = covering;
	}

	public void fillArrays(long[] l, long[] m) {
		Random rnd = new Random(seed);
		int lMax = l.length * sparsity;
		fillArray(l, rnd, lMax);
		int mMax = covering ? (lMax * 2) : (m.length * sparsity);
		fillArray(m, rnd, mMax);
	}

	private void fillArray(long[] array, Random rnd, int max) {
		int min = 1; // never 0, for the benefit of hashtables
		long range = max - min;
		for (int i = 0; i < array.length; ++i) {
			array[i] = nextLong(rnd, range) + min;
		}
	}

	protected static long nextLong(Random rnd, long range) {
		return Math.abs(rnd.nextLong()) % range; // dodgy but close enough
	}

}