Soving the kata Directions Reduction

src/main/java/org/fundacionjala/coding/abel/DirReduction.java

@@ -0,0 +1,61 @@
+package org.fundacionjala.coding.abel;
+
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+
+/**
+ * Once upon a time, on a way through the old wild west,…
+ * … a man was given directions to go from one point to another. The directions were "NORTH", "SOUTH", "WEST", "EAST".
+ * Clearly "NORTH" and "SOUTH" are opposite, "WEST" and "EAST" too. Going to one direction and coming back the opposite
+ * direction is a needless effort. Since this is the wild west, with dreadfull weather and not much water, it's
+ * important to save yourself some energy, otherwise you might die of thirst!
+ * How I crossed the desert the smart way.
+ * Write a function dirReduc which will take an array of strings and returns an array of strings with the needless
+ * directions removed (W<->E or S<->N side by side).
+ * The Haskell version takes a list of directions with data Direction = North | East | West | South. The Clojure
+ * version returns nil when the path is reduced to nothing.
+ * The Rust version takes a slice of enum Direction {NORTH, SOUTH, EAST, WEST}.
+ * Examples
+ * dirReduc(["NORTH", "SOUTH", "SOUTH", "EAST", "WEST", "NORTH", "WEST"]) => ["WEST"]
+ * dirReduc(["NORTH", "SOUTH", "SOUTH", "EAST", "WEST", "NORTH"]) => []
+ * Note
+ * Not all paths can be made simpler. The path ["NORTH", "WEST", "SOUTH", "EAST"] is not reducible.
+ * "NORTH" and "WEST", "WEST" and "SOUTH", "SOUTH" and "EAST" are not directly opposite of each other and can't become
+ * such. Hence the result path is itself : ["NORTH", "WEST", "SOUTH", "EAST"].
+ */
+public final class DirReduction {
+
+    /**
+     * Private constructor.
+     */
+    private DirReduction() {
+
+    }
+
+    /**
+     * Reduce the directions.
+     *
+     * @param arr Array with directions.
+     * @return Array with only neccesary directions.
+     */
+    public static String[] dirReduc(String[] arr) {
+        List<String> actuaList = new LinkedList<>(Arrays.asList(arr));
+        int i = 0;
+        while (i < actuaList.size() - 1) {
+            if (("NORTH".equals(actuaList.get(i)) && "SOUTH".equals(actuaList.get(i + 1)))
+                    || ("SOUTH".equals(actuaList.get(i)) && "NORTH".equals(actuaList.get(i + 1)))
+                    || ("EAST".equals(actuaList.get(i)) && "WEST".equals(actuaList.get(i + 1)))
+                    || ("WEST".equals(actuaList.get(i)) && "EAST".equals(actuaList.get(i + 1)))) {
+                actuaList.remove(i + 1);
+                actuaList.remove(i);
+                if (i > 0) {
+                    i--;
+                }
+            } else {
+                i++;
+            }
+        }
+        return actuaList.toArray(new String[actuaList.size()]);
+    }
+}

src/test/java/org/fundacionjala/coding/abel/DirReductionTest.java

@@ -0,0 +1,50 @@
+package org.fundacionjala.coding.abel;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Modifier;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Test class for Dir Reduction.
+ */
+public class DirReductionTest {
+
+    /**
+     * Test for Private Constructors.
+     *
+     * @throws NoSuchMethodException     Thrown when a particular method cannot be found.
+     * @throws IllegalAccessException    Thrown when an application tries to reflectively create an instance.
+     * @throws InvocationTargetException thrown by an invoked method or constructor.
+     * @throws InstantiationException    Thrown when an application tries to create an instance of a class
+     *                                   using the {@code newInstance} method in class.
+     */
+    @Test
+    public void privateConstructorTest() throws NoSuchMethodException, IllegalAccessException,
+            InvocationTargetException, InstantiationException {
+        Constructor<DirReduction> constructor = DirReduction.class.getDeclaredConstructor();
+        assertTrue(Modifier.isPrivate(constructor.getModifiers()));
+        constructor.setAccessible(true);
+        constructor.newInstance();
+    }
+
+    /**
+     * Tests provided.
+     *
+     * @throws Exception for any exception.
+     */
+    @Test
+    public void testSimpleDirReduc() throws Exception {
+        assertEquals("\"NORTH\", \"SOUTH\", \"SOUTH\", \"EAST\", \"WEST\", \"NORTH\", \"WEST\"",
+                new String[]{"WEST"},
+                DirReduction.dirReduc(new String[]{"NORTH", "SOUTH", "SOUTH", "EAST", "WEST", "NORTH", "WEST"}));
+
+        assertEquals("\"NORTH\", \"WEST\", \"SOUTH\", \"EAST\"",
+                new String[]{"NORTH", "WEST", "SOUTH", "EAST"},
+                DirReduction.dirReduc(new String[]{"NORTH", "WEST", "SOUTH", "EAST"}));
+    }
+}