saddle-points: add to track

config.json

@@ -324,6 +324,11 @@
       "slug": "book-store",
       "difficulty": 1,
       "topics": []
+    },
+    {
+      "slug": "saddle-points",
+      "difficulty": 1,
+      "topics": []
     }
   ],
   "deprecated": [

exercises/saddle-points/build.gradle

@@ -0,0 +1,17 @@
+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/saddle-points/src/example/java/Matrix.java

@@ -0,0 +1,44 @@
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+final class Matrix {
+
+  private final List<List<Integer>> values;
+
+  Matrix(final List<List<Integer>> values) {
+    this.values = values;
+  }
+
+  List<MatrixCoordinate> getSaddlePoints() {
+    final List<MatrixCoordinate> result = new ArrayList<>();
+
+    if (values.isEmpty()) {
+      return result;
+    }
+
+    for (int row = 0; row < values.size(); row++) {
+      for (int column = 0; column < values.get(0).size(); column++) {
+        final int coordinateValue = values.get(row).get(column);
+
+        if (coordinateValue == getRowMax(row) && coordinateValue == getColumnMin(column)) {
+          result.add(new MatrixCoordinate(row, column));
+        }
+      }
+    }
+
+    return result;
+  }
+
+  private int getRowMax(final int row) {
+    return Collections.max(values.get(row));
+  }
+
+  private int getColumnMin(final int column) {
+    return values.stream()
+        .map(row -> row.get(column))
+        .min(Integer::compareTo)
+        .get();
+  }
+
+}

exercises/saddle-points/src/example/java/MatrixCoordinate.java

@@ -0,0 +1,31 @@
+final class MatrixCoordinate {
+
+  private final int row;
+
+  private final int column;
+
+  MatrixCoordinate(final int row, final int column) {
+    this.row = row;
+    this.column = column;
+  }
+
+  // Generated equals and hashcode.
+
+  @Override
+  public boolean equals(final Object o) {
+    if (this == o) return true;
+    if (o == null || getClass() != o.getClass()) return false;
+
+    final MatrixCoordinate that = (MatrixCoordinate) o;
+
+    return row == that.row && column == that.column;
+  }
+
+  @Override
+  public int hashCode() {
+    int result = row;
+    result = 31 * result + column;
+    return result;
+  }
+
+}

exercises/saddle-points/src/main/java/Matrix.java

@@ -0,0 +1,5 @@
+final class Matrix {
+
+
+
+}

exercises/saddle-points/src/main/java/MatrixCoordinate.java

@@ -0,0 +1,31 @@
+final class MatrixCoordinate {
+
+  private final int row;
+
+  private final int column;
+
+  MatrixCoordinate(final int row, final int column) {
+    this.row = row;
+    this.column = column;
+  }
+
+  // Generated equals and hashcode.
+
+  @Override
+  public boolean equals(final Object o) {
+    if (this == o) return true;
+    if (o == null || getClass() != o.getClass()) return false;
+
+    final MatrixCoordinate that = (MatrixCoordinate) o;
+
+    return row == that.row && column == that.column;
+  }
+
+  @Override
+  public int hashCode() {
+    int result = row;
+    result = 31 * result + column;
+    return result;
+  }
+
+}

exercises/saddle-points/src/test/java/MatrixTest.java

@@ -0,0 +1,82 @@
+import org.junit.Ignore;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class MatrixTest {
+
+    @Test
+    public void testCanIdentifySingleSaddlePoint() {
+        Matrix matrix = new Matrix(Arrays.asList(
+            Arrays.asList(9, 8, 7),
+            Arrays.asList(5, 3, 2),
+            Arrays.asList(6, 6, 7)
+        ));
+
+        List<MatrixCoordinate> expectedSaddlePoints = Collections.singletonList(new MatrixCoordinate(1, 0));
+
+        assertEquals(expectedSaddlePoints, matrix.getSaddlePoints());
+    }
+
+    @Ignore
+    @Test
+    public void testCanIdentifyThatEmptyMatrixHasNoSaddlePoints() {
+        Matrix matrix = new Matrix(new ArrayList<>());
+
+        List<MatrixCoordinate> expectedSaddlePoints = new ArrayList<>();
+
+        assertEquals(expectedSaddlePoints, matrix.getSaddlePoints());
+    }
+
+    @Ignore
+    @Test
+    public void testCanIdentifyLackOfSaddlePointsWhenThereAreNone() {
+        Matrix matrix = new Matrix(Arrays.asList(
+            Arrays.asList(1, 2, 3),
+            Arrays.asList(3, 1, 2),
+            Arrays.asList(2, 3, 1)
+        ));
+
+        List<MatrixCoordinate> expectedSaddlePoints = new ArrayList<>();
+
+        assertEquals(expectedSaddlePoints, matrix.getSaddlePoints());
+    }
+
+    @Ignore
+    @Test
+    public void testCanIdentifyMultipleSaddlePoints() {
+        Matrix matrix = new Matrix(Arrays.asList(
+            Arrays.asList(4, 5, 4),
+            Arrays.asList(3, 5, 5),
+            Arrays.asList(1, 5, 4)
+        ));
+
+        List<MatrixCoordinate> expectedSaddlePoints = Arrays.asList(
+            new MatrixCoordinate(0, 1),
+            new MatrixCoordinate(1, 1),
+            new MatrixCoordinate(2, 1)
+        );
+
+        assertEquals(expectedSaddlePoints, matrix.getSaddlePoints());
+    }
+
+    @Ignore
+    @Test
+    public void testCanIdentifySaddlePointInBottomRightCorner() {
+        Matrix matrix = new Matrix(Arrays.asList(
+            Arrays.asList(8, 7, 9),
+            Arrays.asList(6, 7, 6),
+            Arrays.asList(3, 2, 5)
+        ));
+
+        List<MatrixCoordinate> expectedSaddlePoints = Collections.singletonList(new MatrixCoordinate(2, 2));
+
+        assertEquals(expectedSaddlePoints, matrix.getSaddlePoints());
+    }
+
+}

exercises/settings.gradle

@@ -51,6 +51,7 @@ include 'rna-transcription'
 include 'robot-name'
 include 'robot-simulator'
 include 'roman-numerals'
+include 'saddle-points'
 include 'scrabble-score'
 include 'secret-handshake'
 include 'series'