Binary search

config.json

@@ -52,7 +52,8 @@
     "robot-simulator",
     "bracket-push",
     "pythagorean-triplet",
-    "binary-search-tree"
+    "binary-search-tree",
+    "binary-search"
   ],
   "exercises": [
     {
@@ -299,6 +300,11 @@
       "slug": "binary-search-tree",
       "difficulty": 1,
       "topics": []
+    },
+    {
+      "slug": "binary-search",
+      "difficulty": 1,
+      "topics": []
     }
   ],
   "deprecated": [

exercises/binary-search/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/binary-search/src/example/java/BinarySearch.java

@@ -0,0 +1,40 @@
+
+import java.util.List;
+
+public class BinarySearch<T extends Comparable<T>> {
+
+    private List<T> array;
+    private int arraySize;
+
+    public BinarySearch(List<T> array) {
+        this.array = array;
+        this.arraySize = array.size();
+    }
+
+    public int indexOf(T value) {
+        return search(value);
+    }
+
+    public List<T> getArray() {
+        return array;
+    }
+
+    private int search(T value) {
+        int left = 0;
+        int right = this.arraySize - 1;
+        int middle;
+        T element;
+        while (left <= right) {
+            middle = (int) Math.floor(0.5 * (left + right));
+            element = this.array.get(middle);
+            if (value.compareTo(element) > 0) {
+                left = middle + 1;
+            } else if (value.compareTo(element) < 0) {
+                right = middle - 1;
+            } else {
+                return middle;
+            }
+        }
+        return -1;
+    }
+}

exercises/binary-search/src/main/java/BinarySearch.java

@@ -0,0 +1,4 @@
+
+public class BinarySearch {
+
+}

exercises/binary-search/src/test/java/BinarySearchTest.java

@@ -0,0 +1,136 @@
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import static org.junit.Assert.assertEquals;
+import org.junit.Ignore;
+import org.junit.Test;
+
+public class BinarySearchTest {
+
+    public static final List<Integer> EMPTY_LIST
+            = Collections.unmodifiableList(new ArrayList<Integer>(0));
+
+    public static final List<Integer> LIST_OF_UNIT_LENGTH
+            = Collections.unmodifiableList(
+                    Arrays.asList(6)
+            );
+
+    private static final List<Integer> SORTED_LIST
+            = Collections.unmodifiableList(
+                    Arrays.asList(1, 3, 4, 6, 8, 9, 11)
+            );
+
+    public static final List<Integer> SORTED_LIST_OF_ODD_LENGTH
+            = Collections.unmodifiableList(
+                    Arrays.asList(1, 3, 5, 8, 13, 21, 34, 55,
+                            89, 144, 233, 377, 634)
+            );
+
+    public static final List<Integer> SORTED_LIST_OF_EVEN_LENGTH
+            = Collections.unmodifiableList(
+                    Arrays.asList(1, 3, 5, 8, 13, 21, 34, 55,
+                            89, 144, 233, 377)
+            );
+
+    @Test
+    public void findsAValueInAnArrayWithOneElement() {
+        BinarySearch<Integer> sut = new BinarySearch<>(LIST_OF_UNIT_LENGTH);
+        final int value = 6;
+        final int actual = sut.indexOf(value);
+        final int expected = 0;
+        assertEquals(expected, actual);
+    }
+
+    @Ignore
+    @Test
+    public void findsAValueInTheMiddleOfAnArray() {
+        BinarySearch<Integer> sut = new BinarySearch<>(SORTED_LIST);
+        final int value = 6;
+        final int actual = sut.indexOf(value);
+        final int expected = 3;
+        assertEquals(expected, actual);
+    }
+
+    @Ignore
+    @Test
+    public void findsAValueAtTheBeginningOfAnArray() {
+        BinarySearch<Integer> sut = new BinarySearch<>(SORTED_LIST);
+        final int value = 1;
+        final int actual = sut.indexOf(value);
+        final int expected = 0;
+        assertEquals(expected, actual);
+    }
+
+    @Ignore
+    @Test
+    public void findsAValueAtTheEndOfAnArray() {
+        BinarySearch<Integer> sut = new BinarySearch<>(SORTED_LIST);
+        final int value = 11;
+        final int actual = sut.indexOf(value);
+        final int expected = 6;
+        assertEquals(expected, actual);
+    }
+
+    @Ignore
+    @Test
+    public void findsAValueInAnArrayOfOddLength() {
+        BinarySearch<Integer> sut = new BinarySearch<>(SORTED_LIST_OF_ODD_LENGTH);
+        final int value = 144;
+        final int actual = sut.indexOf(value);
+        final int expected = 9;
+        assertEquals(expected, actual);
+    }
+
+    @Ignore
+    @Test
+    public void findsAValueInAnArrayOfEvenLength() {
+        BinarySearch<Integer> sut
+                = new BinarySearch<>(SORTED_LIST_OF_EVEN_LENGTH);
+        final int value = 21;
+        final int actual = sut.indexOf(value);
+        final int expected = 5;
+        assertEquals(expected, actual);
+    }
+
+    @Ignore
+    @Test
+    public void identifiesThatAValueIsNotIncludedInTheArray() {
+        BinarySearch<Integer> sut = new BinarySearch<>(SORTED_LIST);
+        final int value = 7;
+        final int actual = sut.indexOf(value);
+        final int expected = -1;
+        assertEquals(expected, actual);
+    }
+
+    @Ignore
+    @Test
+    public void aValueSmallerThanTheArraysSmallestValueIsNotIncluded() {
+        BinarySearch<Integer> sut = new BinarySearch<>(SORTED_LIST);
+        final int value = 0;
+        final int actual = sut.indexOf(value);
+        final int expected = -1;
+        assertEquals(expected, actual);
+    }
+
+    @Ignore
+    @Test
+    public void aValueLargerThanTheArraysSmallestValueIsNotIncluded() {
+        BinarySearch<Integer> sut = new BinarySearch<>(SORTED_LIST);
+        final int value = 13;
+        final int actual = sut.indexOf(value);
+        final int expected = -1;
+        assertEquals(expected, actual);
+    }
+
+    @Ignore
+    @Test
+    public void nothingIsIncludedInAnEmptyArray() {
+        BinarySearch<Integer> sut = new BinarySearch<>(EMPTY_LIST);
+        final int value = 1;
+        final int actual = sut.indexOf(value);
+        final int expected = -1;
+        assertEquals(expected, actual);
+    }
+}