2016 Update

Task/Ray-casting-algorithm/Java/ray-casting-algorithm.java

@@ -0,0 +1,56 @@
+import static java.lang.Math.*;
+
+public class RayCasting {
+
+    static boolean intersects(int[] A, int[] B, double[] P) {
+        if (A[1] > B[1])
+            return intersects(B, A, P);
+
+        if (P[1] == A[1] || P[1] == B[1])
+            P[1] += 0.0001;
+
+        if (P[1] > B[1] || P[1] < A[1] || P[0] > max(A[0], B[0]))
+            return false;
+
+        if (P[0] < min(A[0], B[0]))
+            return true;
+
+        double red = (P[1] - A[1]) / (double) (P[0] - A[0]);
+        double blue = (B[1] - A[1]) / (double) (B[0] - A[0]);
+        return red >= blue;
+    }
+
+    static boolean contains(int[][] shape, double[] pnt) {
+        boolean inside = false;
+        int len = shape.length;
+        for (int i = 0; i < len; i++) {
+            if (intersects(shape[i], shape[(i + 1) % len], pnt))
+                inside = !inside;
+        }
+        return inside;
+    }
+
+    public static void main(String[] a) {
+        double[][] testPoints = {{10, 10}, {10, 16}, {-20, 10}, {0, 10},
+        {20, 10}, {16, 10}, {20, 20}};
+
+        for (int[][] shape : shapes) {
+            for (double[] pnt : testPoints)
+                System.out.printf("%7s ", contains(shape, pnt));
+            System.out.println();
+        }
+    }
+
+    final static int[][] square = {{0, 0}, {20, 0}, {20, 20}, {0, 20}};
+
+    final static int[][] squareHole = {{0, 0}, {20, 0}, {20, 20}, {0, 20},
+    {5, 5}, {15, 5}, {15, 15}, {5, 15}};
+
+    final static int[][] strange = {{0, 0}, {5, 5}, {0, 20}, {5, 15}, {15, 15},
+    {20, 20}, {20, 0}};
+
+    final static int[][] hexagon = {{6, 0}, {14, 0}, {20, 10}, {14, 20},
+    {6, 20}, {0, 10}};
+
+    final static int[][][] shapes = {square, squareHole, strange, hexagon};
+}