sequential now works flawlessly

inf2440/hw4/Oblig4.java

@@ -48,6 +48,16 @@ abstract class Oblig4 {
 		return (a * x[p3]) + (b * y[p3]) + c;
 	}
 
+	// Distance between two points
+	double pointDist(int p1, int p2) {
+		int x1 = x[p1], y1 = y[p1];
+		int x2 = x[p2], y2 = y[p2];
+
+		int dx = x2 - x1;
+		int dy = y2 - y1;
+		return Math.abs(Math.sqrt((dx * dx) + (dy * dy)));
+	}
+
 	// Distance between the line and p3
 	double dist(double l, int a, int b) {
 		return l / Math.sqrt((a * a) + (b * b));

inf2440/hw4/Sequential.java

@@ -10,8 +10,12 @@ class Sequential extends Oblig4 {
 		MAX_X = x[maxX];
 		MAX_Y = y[maxY];
 
-		coHull = pointsRightOf(maxX, minX);
-		coHull.append(pointsRightOf(minX, maxX));
+		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)+" ");
@@ -40,7 +44,57 @@ class Sequential extends Oblig4 {
 		}
 	}
 
-	IntList pointsRightOf(int p1, int p2) {
+	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;
 
@@ -48,29 +102,35 @@ class Sequential extends Oblig4 {
 		int b = lineB(p1, p2);
 		int c = lineC(p1, p2);
 
-		for (int i = 0; i < n; ++i) {
-			if (i == p1 || i == 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, i);
+			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 = i;
+				p3 = idx;
 			}
 		}
 
 		if (p3 == -1) {
-			IntList l = new IntList(2);
-			l.add(p1);
+			IntList l = addPointsOnLine(nwIndexes, a, b, c, p1);
+			l.add(p2);
+
 			return l;
 		}
 
-		IntList l = pointsRightOf(p1, p3);
-		l.append(pointsRightOf(p3, p2));
+		IntList l = pointsRightOf(p1, p3, nwIndexes);
+		l.append(pointsRightOf(p3, p2, nwIndexes));
 		return l;
 	}
 }