Java Convex Polygon benchmark code

[nit.git] / benchmarks / polygons / java / code / AntiClockSort.java

diff --git a/benchmarks/polygons/java/code/AntiClockSort.java b/benchmarks/polygons/java/code/AntiClockSort.java
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+
+/**
+ *
+ * @author Johan
+ * @source
+ * http://stackoverflow.com/questions/6989100/sort-points-in-clockwise-order
+ */
+public class AntiClockSort extends PolygonSorter {
+
+    public AntiClockSort(double[][] points) {
+        super(points);
+    }
+
+    /**
+     * Compare polygon vertices in counter-clock wise order starting at six
+     * hour. If two points share the same rad, then the farest to the center is
+     * chosen.
+     *
+     * @param a: a point to compare
+     * @param b: a second point to compare
+     * @return
+     */
+    @Override
+    public int compare(PointDouble a, PointDouble b) {
+        if (a.x - center.x >= 0 && b.x - center.x < 0) {
+            return -1;
+        }
+        if (a.x - center.x < 0 && b.x - center.x >= 0) {
+            return +1;
+        }
+        if (a.x - center.x == 0 && b.x - center.x == 0) {
+            if (a.y - center.y >= 0 || b.y - center.y >= 0) {
+                return (a.y > b.y) ? -1 : +1;
+            }
+            return (b.y > a.y) ? -1 : +1;
+        }
+
+        // compute the cross product of vectors (center -> a) x (center -> b)
+        double det = (a.x - center.x) * (b.y - center.y) - (b.x - center.x) * (a.y - center.y);
+        if (det < 0) {
+            return -1;
+        }
+        if (det > 0) {
+            return +1;
+        }
+
+        // points a and b are on the same line from the center
+        // check which point is closer to the center
+        double d1 = (a.x - center.x) * (a.x - center.x) + (a.y - center.y) * (a.y - center.y);
+        double d2 = (b.x - center.x) * (b.x - center.x) + (b.y - center.y) * (b.y - center.y);
+        return (d1 > d2) ? -1 : +1;
+    }
+}