largest-series-product: add to track

config.json

@@ -43,7 +43,8 @@
     "nth-prime",
     "pascals-triangle",
     "beer-song",
-    "difference-of-squares"
+    "difference-of-squares",
+    "largest-series-product"
   ],
   "exercises": [
     {
@@ -245,6 +246,11 @@
       "slug": "difference-of-squares",
       "difficulty": 1,
       "topics": []
+    },
+    {
+      "slug": "largest-series-product",
+      "difficulty": 1,
+      "topics": []
     }
   ],
   "deprecated": [

exercises/largest-series-product/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/largest-series-product/src/example/java/LargestSeriesProductCalculator.java

@@ -0,0 +1,56 @@
+public final class LargestSeriesProductCalculator {
+
+    private final String stringToSearch;
+
+    public LargestSeriesProductCalculator(final String stringToSearch) throws IllegalArgumentException {
+        this.stringToSearch = stringToSearch;
+        validateStringToSearch();
+    }
+
+    public long calculateLargestProductForSeriesLength(final int seriesLength) throws IllegalArgumentException {
+        if (seriesLength < 0) {
+            throw new IllegalArgumentException("Series length must be non-negative.");
+        } else if (seriesLength == 0) {
+            return 1;
+        } else if (seriesLength > stringToSearch.length()) {
+            throw new IllegalArgumentException(
+                    "Series length must be less than or equal to the length of the string to search.");
+        } else {
+            long result = 0;
+
+            int numberOfSeriesToCheck = stringToSearch.length() - seriesLength + 1;
+
+            for (int startIndex = 0; startIndex < numberOfSeriesToCheck; startIndex++) {
+                /*
+                 * Note: computing the product of each series fresh each time is not the most efficient solution, but
+                 * it's the simplest to reason about.
+                 */
+                result = Math.max(result, computeProductOfSeries(startIndex, seriesLength));
+            }
+
+            return result;
+        }
+    }
+
+    private void validateStringToSearch() throws IllegalArgumentException {
+        if (stringToSearch == null) {
+            throw new IllegalArgumentException("String to search must be non-null.");
+        } else if (!stringToSearch.chars().allMatch(Character::isDigit)) {
+            throw new IllegalArgumentException("String to search may only contains digits.");
+        }
+    }
+
+    private long computeProductOfSeries(final int startIndex, final int seriesLength) {
+        // The multiplicative identity is 1.
+        long result = 1;
+
+        final int endIndex = startIndex + seriesLength - 1;
+
+        for (int characterIndex = startIndex; characterIndex <= endIndex; characterIndex++) {
+            result = result * Character.getNumericValue(stringToSearch.charAt(characterIndex));
+        }
+
+        return result;
+    }
+
+}

exercises/largest-series-product/src/main/java/LargestSeriesProductCalculator.java

@@ -0,0 +1,5 @@
+public class LargestSeriesProductCalculator {
+
+
+
+}

exercises/largest-series-product/src/test/java/LargestSeriesProductCalculatorTest.java

@@ -0,0 +1,218 @@
+import org.junit.Ignore;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import static org.junit.Assert.assertEquals;
+
+public final class LargestSeriesProductCalculatorTest {
+
+    /*
+     * See https://github.com/junit-team/junit4/wiki/Rules for information on JUnit Rules in general and
+     * ExpectedExceptions in particular.
+     */
+    @Rule
+    public ExpectedException expectedException = ExpectedException.none();
+
+    @Test
+    public void testCorrectlyCalculatesLargestProductOfLengthTwoWithNumbersInOrder() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("0123456789");
+        final long expectedProduct = 72;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(2);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductOfLengthTwoWithNumbersNotInOrder() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("576802143");
+        final long expectedProduct = 48;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(2);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductWhenSeriesLengthEqualsStringToSearchLength() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("29");
+        final long expectedProduct = 18;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(2);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductOfLengthThreeWithNumbersInOrder() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("0123456789");
+        final long expectedProduct = 504;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(3);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductOfLengthThreeWithNumbersNotInOrder() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("1027839564");
+        final long expectedProduct = 270;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(3);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductOfLengthFiveWithNumbersInOrder() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("0123456789");
+        final long expectedProduct = 15120;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(5);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductInLongStringToSearchV1() {
+        final LargestSeriesProductCalculator calculator
+                = new LargestSeriesProductCalculator("73167176531330624919225119674426574742355349194934");
+
+        final long expectedProduct = 23520;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(6);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductInLongStringToSearchV2() {
+        final LargestSeriesProductCalculator calculator
+                = new LargestSeriesProductCalculator("52677741234314237566414902593461595376319419139427");
+
+        final long expectedProduct = 28350;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(6);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductInLongStringToSearchFromProjectEuler() {
+        final LargestSeriesProductCalculator calculator
+                = new LargestSeriesProductCalculator("7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450");
+
+        final long expectedProduct = 23514624000L;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(13);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductOfZeroIfAllDigitsAreZeroes() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("0000");
+        final long expectedProduct = 0;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(2);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductOfZeroIfAllSeriesOfGivenLengthContainZero() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("99099");
+        final long expectedProduct = 0;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(3);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testSeriesLengthLongerThanLengthOfStringToTestIsRejected() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("123");
+
+        expectedException.expect(IllegalArgumentException.class);
+        expectedException.expectMessage(
+                "Series length must be less than or equal to the length of the string to search.");
+
+        calculator.calculateLargestProductForSeriesLength(4);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductOfLength0ForEmptyStringToSearch() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("");
+        final long expectedProduct = 1;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(0);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testCorrectlyCalculatesLargestProductOfLength0ForNonEmptyStringToSearch() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("123");
+        final long expectedProduct = 1;
+
+        final long actualProduct = calculator.calculateLargestProductForSeriesLength(0);
+
+        assertEquals(expectedProduct, actualProduct);
+    }
+
+    @Ignore
+    @Test
+    public void testEmptyStringToSearchAndSeriesOfNonZeroLengthIsRejected() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("");
+
+        expectedException.expect(IllegalArgumentException.class);
+        expectedException.expectMessage(
+                "Series length must be less than or equal to the length of the string to search.");
+
+        calculator.calculateLargestProductForSeriesLength(1);
+    }
+
+    @Ignore
+    @Test
+    public void testStringToSearchContainingNonDigitCharacterIsRejected() {
+        expectedException.expect(IllegalArgumentException.class);
+        expectedException.expectMessage("String to search may only contains digits.");
+
+        new LargestSeriesProductCalculator("1234a5");
+    }
+
+    @Ignore
+    @Test
+    public void testNegativeSeriesLengthIsRejected() {
+        final LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("12345");
+
+        expectedException.expect(IllegalArgumentException.class);
+        expectedException.expectMessage("Series length must be non-negative.");
+
+        calculator.calculateLargestProductForSeriesLength(-1);
+    }
+
+    @Ignore
+    @Test
+    public void testNullStringToSearchIsRejected() {
+        expectedException.expect(IllegalArgumentException.class);
+        expectedException.expectMessage("String to search must be non-null.");
+
+        new LargestSeriesProductCalculator(null);
+    }
+
+}

exercises/settings.gradle

@@ -14,6 +14,7 @@ include 'grade-school'
 include 'hamming'
 include 'hexadecimal'
 include 'hello-world'
+include 'largest-series-product'
 include 'linked-list'
 include 'luhn'
 include 'meetup'