uni/inf2440/hw4/Sequential.java

class Sequential extends Oblig4 {
	Sequential(NPunkter17 points) {
		super(points);
		name = "Sequential";
	}

	@Override
	void solve() {
		findMinMaxXY();
		MAX_X = x[maxX];
		MAX_Y = y[maxY];

		IntList indexes = new IntList(n);
		for (int i = 0; i < n; ++i)
			indexes.add(i);

		coHull = pointsRightOf(maxX, minX, indexes);
		coHull.append(pointsRightOf(minX, maxX, indexes));

		for (int i = 0; i < coHull.size(); ++i) {
			System.out.print(coHull.get(i)+" ");
		}
		System.out.println("");
	}

	void findMinMaxXY() {
		minX = 0;
		maxX = 0;
		minY = 0;
		maxY = 0;

		for (int i = 1; i < n; ++i) {
			int px = x[i];
			if (px < x[minX])
				minX = i;
			if (px > x[maxX])
				maxX = i;

			int py = y[i];
			if (py < y[minY])
				minY = i;
			if (py > y[maxY])
				maxY = i;
		}
	}

	IntList addPointsOnLine(IntList indexes, int a, int b, int c, int p1) {
		IntList l = new IntList();

		// Add points on the line between p1 and p2
		for (int i = 0; i < indexes.size(); ++i) {
			int idx = indexes.get(i);

			double line = lineEquation(a, b, c, idx);
			if (line == 0)
				l.add(idx);
		}

		// Calculate distances for sorting
		double[] dists = new double[l.size()];
		for (int i = 0; i < l.size(); ++i) {
			dists[i] = pointDist(p1, l.get(i));
		}

		// Sort points based on distance from p1
		// (Bubble sort, but it's usually really few elements)
		boolean sorted;
		do {
			sorted = true;

			// Loop through points, swap non-sorted ones
			for (int i = 1; i < l.size(); ++i) {
				double dist = dists[i];
				double prevDist = dists[i - 1];

				// Skip if already sorted
				if (prevDist <= dist)
					continue;

				sorted = false;

				// Swap indexes
				int tmpi = l.data[i];
				l.data[i] = l.data[i - 1];
				l.data[i - 1] = tmpi;

				// Swap distances
				double tmpd = dists[i];
				dists[i] = dists[i - 1];
				dists[i - 1] = tmpd;
			}
		} while (!sorted);

		return l;
	}

	IntList pointsRightOf(int p1, int p2, IntList indexes) {
		int p3 = -1;
		double p3dist = 0;

		int a = lineA(p1, p2);
		int b = lineB(p1, p2);
		int c = lineC(p1, p2);

		IntList nwIndexes = new IntList();

		for (int i = 0; i < indexes.size(); ++i) {
			int idx = indexes.get(i);
			if (idx == p1 || idx == p2)
				continue;

			double line = lineEquation(a, b, c, idx);
			if (line > 0)
				continue;

			nwIndexes.add(idx);

			double dist = Math.abs(dist(line, a, b));
			if (dist > p3dist) {
				p3dist = dist;
				p3 = idx;
			}
		}

		if (p3 == -1) {
			IntList l = addPointsOnLine(nwIndexes, a, b, c, p1);
			l.add(p2);

			return l;
		}

		IntList l = pointsRightOf(p1, p3, nwIndexes);
		l.append(pointsRightOf(p3, p2, nwIndexes));
		return l;
	}
}