feat: add distance method to Vector3

src/main/java/com/adventofcode/flashk/common/Vector3.java

@@ -51,7 +51,16 @@ public static Vector3 transform(Vector3 start, Vector3 end) {
 
 		return new Vector3(x,y,z);
 	}
-
+
+    public static double distance(Vector3 a, Vector3 b) {
+
+        int xDiff = b.x - a.x;
+        int yDiff = b.y - a.y;
+        int zDiff = b.z - a.z;
+
+        return Math.sqrt(Math.pow(xDiff, 2) + Math.pow(yDiff, 2) + Math.pow(zDiff,2));
+    }
+
 	/// Shorthand for `Vector3(-1,0,0)`.
     /// @return A unitary vector that points to the left.
 	public static Vector3 left() {

src/test/java/com/adventofcode/flashk/common/Vector3Test.java

@@ -69,6 +69,95 @@ void transformStaticTest() {
         assertEquals(-1, direction.getZ());
     }
 
+    @Test
+    void testDistanceMainAxis() {
+
+        // Arrange - X axis
+        Vector3 a = new Vector3(0, 0, 0);
+        Vector3 b = new Vector3(5, 0, 0);
+        double expectedX = 5.0;
+
+        // Act & Assert - X Axis
+        double actualX = Vector3.distance(a, b);
+        assertEquals(expectedX, actualX);
+
+        // Arrange - Y axis
+        a = new Vector3(1, 1, 1);
+        b = new Vector3(1, 11, 1);
+        double expectedY = 10.0;
+
+        // Act & Assert - Y axis
+        double actualY = Vector3.distance(a, b);
+        assertEquals(expectedY, actualY);
+
+        // Arrange - Z axis
+        Vector3 v1 = new Vector3(2,5,8);
+        Vector3 v2 = new Vector3(2,5,5);
+        double expectedZ = 3;
+
+        // Act & Assert - Z axis
+        double actualZ = Vector3.distance(v1, v2);
+        assertEquals(expectedZ, actualZ);
+    }
+
+    @Test
+    void testDistance2D() {
+        // 1. Arrange
+        Vector3 a = new Vector3(0, 0, 0);
+        Vector3 b = new Vector3(3, 4, 0);
+        double expected = 5.0;
+
+        // 2. Act
+        double actual = Vector3.distance(a, b);
+
+        // 3. Assert
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    void testDistanceSame() {
+
+        // 1. Arrange
+        Vector3 a = new Vector3(100, 50, -25);
+        Vector3 b = new Vector3(100, 50, -25);
+        double expected = 0;
+
+        // 2. Act
+        double actual = Vector3.distance(a, b);
+
+        // 3. Assert
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    void testDistance() {
+        // 1. Arrange
+        Vector3 a = new Vector3(2, 8, 3);
+        Vector3 b = new Vector3(7, 1, 9);
+
+        double expected = Math.sqrt(110);
+
+        // 2. Act
+        double actual = Vector3.distance(a, b);
+
+        // 3. Assert
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    void testDistanceNegatives() {
+        // 1. Arrange
+        Vector3 a = new Vector3(1, 1, 1);
+        Vector3 b = new Vector3(-3, -2, 7);
+        double expected = Math.sqrt(61);
+
+        // 2. Act
+        double actual = Vector3.distance(a, b);
+
+        // 3. Assert
+        assertEquals(expected, actual);
+    }
+
     @Test
     void leftTest() {