Do not teleport across gaps of size one

src/edu/kit/informatik/MainTest.java

@@ -128,6 +128,11 @@ class MainTest {
         cmpInOut("spt_input.txt", "spt_output.txt");
     }
 
+    @Test
+    void fuzz12() throws IOException {
+        cmpInOut("fuzz12_input.txt", "fuzz12_output.txt");
+    }
+
     private void cmpInOut(String in, String out) throws IOException {
         System.setIn(new ByteArrayInputStream(readFile(in)));
         ByteArrayOutputStream output = new ByteArrayOutputStream();

src/edu/kit/informatik/model/RailwayNetwork.java

@@ -2,6 +2,7 @@ package edu.kit.informatik.model;
 
 import edu.kit.informatik.ui.InvalidInputException;
 
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedList;
@@ -207,13 +208,6 @@ public class RailwayNetwork {
             return containingRail.get().move(position, direction, steps);
         }
         final Rail[] touchingRails = findTouchingRails(position);
-        final Vector2D nextPossiblePosition = position.add(direction);
-        final Optional<Rail> possibleContainingRail = findRailPotentiallyContaining(nextPossiblePosition);
-        if (possibleContainingRail.isPresent()
-                && !possibleContainingRail.get().contains(position.subtract(direction))) {
-            return possibleContainingRail.get().move(position, direction, steps);
-             
-        }
         if (touchingRails.length == 0) {
             return null;
         } else if (touchingRails.length == 1) {
@@ -221,12 +215,14 @@ public class RailwayNetwork {
         }
         final Vector2D onRailOne = touchingRails[0].move(position, new Vector2D(direction), steps);
         final Vector2D onRailTwo = touchingRails[1].move(position, new Vector2D(direction), steps);
-        if (position.equals(onRailOne) || onRailOne == null) {
+        if (position.equals(onRailOne) || onRailOne == null
+            || (onRailTwo != null && onRailTwo.subtract(position).directionEquals(direction))) {
             // we are moving on rail two
             final Vector2D newDirection = touchingRails[1].getDirectionFrom(position);
             direction.copyFrom(newDirection);
             return onRailTwo;
-        } else if (position.equals(onRailTwo) || onRailTwo == null) {
+        } else if (position.equals(onRailTwo) || onRailTwo == null
+            || onRailOne.subtract(position).directionEquals(direction)) {
             final Vector2D newDirection = touchingRails[0].getDirectionFrom(position);
             direction.copyFrom(newDirection);
             return onRailOne;

src/edu/kit/informatik/model/Vector2D.java

@@ -67,13 +67,26 @@ public class Vector2D {
      * Check whether this vector is parallel to another vector. Note that this method only works for vectors that
      * are parallel to one of the coordinate axes.
      *
-     * @param other the point to measure distance to
-     * @return the manhattan distance
+     * @param other vector to compare
+     * @return whether both are parallel
      */
     public boolean isParallelTo(Vector2D other) {
         return x == 0 && other.x == 0 || y == 0 && other.y == 0;
     }
 
+    /**
+     * Calculate whether this vector points in the same direction as another. Note that this method only works for
+     * vectors that are parallel to one of the coordinate axes.
+     *
+     * @param other vector to compare
+     * @return whether they represent the same direction
+     */
+    public boolean directionEquals(Vector2D other) {
+        return x == 0 && x == other.x && Long.signum(y) == Long.signum(other.y)
+            || y == 0 && y == other.y && Long.signum(x) == Long.signum(other.x);
+    }
+
+
     /**
      * Normalize this vector. Will essentially return a new vector with (x/|x|, y/|y|).
      *