spiral-matrix: add to track

config.json

@@ -284,6 +284,13 @@
 
       ]
     },
+    {
+      "slug": "spiral-matrix",
+      "difficulty": 6,
+      "topics": [
+
+      ]
+    },
     {
       "slug": "roman-numerals",
       "difficulty": 6,

exercises/settings.gradle

@@ -65,6 +65,7 @@ include 'sieve'
 include 'simple-cipher'
 include 'simple-linked-list'
 include 'space-age'
+include 'spiral-matrix'
 include 'strain'
 include 'sublist'
 include 'sum-of-multiples'

exercises/spiral-matrix/build.gradle

@@ -0,0 +1,18 @@
+apply plugin: "java"
+apply plugin: "eclipse"
+apply plugin: "idea"
+
+repositories {
+  mavenCentral()
+}
+
+dependencies {
+  testCompile "junit:junit:4.12"
+}
+
+test {
+  testLogging {
+    exceptionFormat = 'full'
+    events = ["passed", "failed", "skipped"]
+  }
+}

exercises/spiral-matrix/src/example/java/Coordinate.java

@@ -0,0 +1,31 @@
+class Coordinate {
+
+    private final int x;
+
+    private final int y;
+
+    Coordinate(int x, int y) {
+        this.x = x;
+        this.y = y;
+    }
+
+    int getX() {
+        return x;
+    }
+
+    int getY() {
+        return y;
+    }
+
+    Coordinate step(Direction direction) {
+        return new Coordinate(x + direction.getDx(), y + direction.getDy());
+    }
+
+    boolean isWithinGridOfSize(int size) {
+        return x >= 0
+                && x < size
+                && y >= 0
+                && y < size;
+    }
+
+}

exercises/spiral-matrix/src/example/java/Direction.java

@@ -0,0 +1,29 @@
+enum Direction {
+
+    UP   ( 0, -1),
+    RIGHT( 1,  0),
+    DOWN ( 0,  1),
+    LEFT (-1,  0);
+
+    private final int dx;
+
+    private final int dy;
+
+    Direction(int dx, int dy) {
+        this.dx = dx;
+        this.dy = dy;
+    }
+
+    int getDx() {
+        return dx;
+    }
+
+    int getDy() {
+        return dy;
+    }
+
+    Direction turnRight() {
+        return Direction.values()[(ordinal() + 1) % Direction.values().length];
+    }
+
+}

exercises/spiral-matrix/src/example/java/SpiralMatrixBuilder.java

@@ -0,0 +1,29 @@
+class SpiralMatrixBuilder {
+
+    int[][] buildMatrixOfSize(int size) {
+        if (size == 0) {
+            return new int[][]{};
+        }
+
+        int[][] result = new int[size][size];
+        int entryCount = (int) Math.pow(size, 2.0);
+
+        Coordinate coord = new Coordinate(0, 0);
+        Direction direction = Direction.RIGHT;
+
+        for (int i = 0; i < entryCount; i++) {
+            result[coord.getY()][coord.getX()] = i + 1;
+
+            Coordinate maybeNextCoord = coord.step(direction);
+            if (maybeNextCoord.isWithinGridOfSize(size) && result[maybeNextCoord.getY()][maybeNextCoord.getX()] == 0) {
+                coord = maybeNextCoord;
+            } else {
+                direction = direction.turnRight();
+                coord = coord.step(direction);
+            }
+        }
+
+        return result;
+    }
+
+}

exercises/spiral-matrix/src/test/java/SpiralMatrixBuilderTest.java

@@ -0,0 +1,86 @@
+import org.junit.Before;
+import org.junit.Ignore;
+import org.junit.Test;
+
+import static org.junit.Assert.assertArrayEquals;
+
+/*
+ * version: 1.0.0
+ */
+public class SpiralMatrixBuilderTest {
+
+    private SpiralMatrixBuilder spiralMatrixBuilder;
+
+    @Before
+    public void setUp() {
+        spiralMatrixBuilder = new SpiralMatrixBuilder();
+    }
+
+    @Test
+    public void testEmptySpiral() {
+        int[][] expected = {};
+
+        assertArrayEquals(expected, spiralMatrixBuilder.buildMatrixOfSize(0));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void testTrivialSpiral() {
+        int[][] expected = {
+                {1}
+        };
+
+        assertArrayEquals(expected, spiralMatrixBuilder.buildMatrixOfSize(1));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void testSpiralOfSize2() {
+        int[][] expected = {
+                {1, 2},
+                {4, 3}
+        };
+
+        assertArrayEquals(expected, spiralMatrixBuilder.buildMatrixOfSize(2));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void testSpiralOfSize3() {
+        int[][] expected = {
+                {1, 2, 3},
+                {8, 9, 4},
+                {7, 6, 5}
+        };
+
+        assertArrayEquals(expected, spiralMatrixBuilder.buildMatrixOfSize(3));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void testSpiralOfSize4() {
+        int[][] expected = {
+                { 1,  2,  3,  4},
+                {12, 13, 14,  5},
+                {11, 16, 15,  6},
+                {10,  9,  8,  7}
+        };
+
+        assertArrayEquals(expected, spiralMatrixBuilder.buildMatrixOfSize(4));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void testSpiralOfSize5() {
+        int[][] expected = {
+                { 1,  2,  3,  4,  5},
+                {16, 17, 18, 19,  6},
+                {15, 24, 25, 20,  7},
+                {14, 23, 22, 21,  8},
+                {13, 12, 11, 10,  9}
+        };
+
+        assertArrayEquals(expected, spiralMatrixBuilder.buildMatrixOfSize(5));
+    }
+
+}