Added Array zero mover exercise.

stringbasic · stringbasic · commit 6e68b5a6e368 · 2020-01-04T21:28:46.000Z
diff --git a/src/main/java/stringbasic/exercises/ArrayZeroTail.java b/src/main/java/stringbasic/exercises/ArrayZeroTail.java
@@ -0,0 +1,25 @@
+package stringbasic.exercises;
+
+import java.util.Arrays;
+
+/**
+ * Moves all zeros in an array to the end
+ */
+public class ArrayZeroTail {
+    public static int[] moveZeros(int [] elements) {
+        int [] result = Arrays.copyOf(elements, elements.length);
+        for (int i = 0, j = -1; i < result.length; i++) {
+            if (result[i] != 0 && i>j && j>=0) {
+                /* switch with last 0 found */
+                result[j] = result[i];
+                result[i] = 0;
+                j++;
+            } else if (result[i] == 0 && j<0) {
+                /* first 0 element */
+                j=0;
+            }
+        }
+
+        return result;
+    }
+}
diff --git a/src/test/java/stringbasic/exercises/ArrayZeroTailTest.java b/src/test/java/stringbasic/exercises/ArrayZeroTailTest.java
@@ -0,0 +1,33 @@
+package stringbasic.exercises;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class ArrayZeroTailTest {
+    @Test
+    public void testEmptyArray() {
+        int[] emptyArray = {};
+        Assert.assertArrayEquals("expect empty array", emptyArray, ArrayZeroTail.moveZeros(emptyArray));
+    }
+
+    @Test
+    public void testNoZerosArray() {
+        int[] valuesArray = {1,2,4};
+        Assert.assertArrayEquals("expect equal array", valuesArray, ArrayZeroTail.moveZeros(valuesArray));
+    }
+
+    @Test
+    public void testZerosAtEndArray() {
+        int[] valuesArray = {1,2,4,0,0};
+        Assert.assertArrayEquals("expect equal array", valuesArray, ArrayZeroTail.moveZeros((valuesArray)));
+    }
+
+    @Test
+    public void testZerosUnsortedArray() {
+        int[] valuesArray = {0,1,4,0,2,0};
+        int[] originalArray = {0,1,4,0,2,0};
+        int[] expectedArray = {1,4,2,0,0,0};
+        Assert.assertArrayEquals("expect equal array", expectedArray, ArrayZeroTail.moveZeros((valuesArray)));
+        Assert.assertArrayEquals("original array is unchanged", valuesArray, originalArray);
+    }
+}
