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Adding the grain exercise. (exercism#1755)
* Start adding the exercise. * Add entry in the gradle project for the exercise. * Update the README. * Implement the tests and the basic structure of the class for this exercise. * Set the correct version. * Pass checkstyle. * Provide reference implementation. * Correct code. * Correct reference implementation. * Apply PR suggestions. * Fix order of annotations and remove comments. * Review the level of the exercise. * Correct the position of the exercise in the config. * Correct assertion param orders and do not use static methods. * Update error assertions to ExpectedException.
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‎config.json‎

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"randomness"
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]
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},
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{
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"slug": "grains",
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"uuid": "5ee66f39-5e37-4907-a6d9-f55d38324c6c",
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"core": false,
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"unlocked_by": "two-fer",
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"difficulty": 2,
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"topics": [
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"loops",
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"math"
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],
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"deprecated": false
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},
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{
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"slug": "pangram",
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"uuid": "133b0f84-bdc7-4508-a0a1-5732a7db81ef",

‎exercises/grains/.meta/src/reference/java/Grains.java‎

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import java.math.BigInteger;
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import java.util.stream.IntStream;
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class Grains {
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BigInteger computeNumberOfGrainsOnSquare(final int square) {
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if (1 <= square && square <= 64) {
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return BigInteger.valueOf(2).pow(square - 1);
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} else {
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throw new IllegalArgumentException("square must be between 1 and 64");
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}
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}
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BigInteger computeTotalNumberOfGrainsOnBoard() {
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return IntStream.rangeClosed(1, 64)
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.mapToObj(this::computeNumberOfGrainsOnSquare)
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.reduce(
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BigInteger.valueOf(0),
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BigInteger::add);
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}
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}

‎exercises/grains/.meta/version‎

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1.2.0

‎exercises/grains/README.md‎

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# Grains
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Calculate the number of grains of wheat on a chessboard given that the number
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on each square doubles.
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There once was a wise servant who saved the life of a prince. The king
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promised to pay whatever the servant could dream up. Knowing that the
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king loved chess, the servant told the king he would like to have grains
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of wheat. One grain on the first square of a chess board, with the number
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of grains doubling on each successive square.
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There are 64 squares on a chessboard (where square 1 has one grain, square 2 has two grains, and so on).
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Write code that shows:
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- how many grains were on a given square, and
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- the total number of grains on the chessboard
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## For bonus points
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Did you get the tests passing and the code clean? If you want to, these
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are some additional things you could try:
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- Optimize for speed.
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- Optimize for readability.
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Then please share your thoughts in a comment on the submission. Did this
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experiment make the code better? Worse? Did you learn anything from it?
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## Setup
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Go through the setup instructions for Java to install the necessary
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dependencies:
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[https://exercism.io/tracks/java/installation](https://exercism.io/tracks/java/installation)
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# Running the tests
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You can run all the tests for an exercise by entering the following in your
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terminal:
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```sh
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$ gradle test
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```
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> Use `gradlew.bat` if you're on Windows
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In the test suites all tests but the first have been skipped.
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Once you get a test passing, you can enable the next one by removing the
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`@Ignore("Remove to run test")` annotation.
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## Source
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JavaRanch Cattle Drive, exercise 6 [http://www.javaranch.com/grains.jsp](http://www.javaranch.com/grains.jsp)
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## Submitting Incomplete Solutions
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It's possible to submit an incomplete solution so you can see how others have
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completed the exercise.

‎exercises/grains/build.gradle‎

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

‎exercises/grains/src/main/java/Grains.java‎

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import java.math.BigInteger;
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class Grains {
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BigInteger computeNumberOfGrainsOnSquare(final int square) {
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throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
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}
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BigInteger computeTotalNumberOfGrainsOnBoard() {
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throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
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}
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}

‎exercises/grains/src/test/java/GrainsTest.java‎

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import org.junit.Before;
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import org.junit.Ignore;
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import org.junit.Rule;
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import org.junit.Test;
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import org.junit.rules.ExpectedException;
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import java.math.BigInteger;
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import static org.junit.Assert.assertEquals;
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public class GrainsTest {
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private static String wrongSquareMessage = "square must be between 1 and 64";
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@Rule
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public ExpectedException expectedException = ExpectedException.none();
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private Grains grains;
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@Before
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public void setup() {
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grains = new Grains();
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}
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@Test
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public void countAtSquare1() {
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BigInteger result = grains.computeNumberOfGrainsOnSquare(1);
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assertEquals(new BigInteger("1"), result);
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}
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@Ignore("Remove to run test")
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@Test
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public void countAtSquare2() {
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BigInteger result = grains.computeNumberOfGrainsOnSquare(2);
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assertEquals(new BigInteger("2"), result);
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}
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@Ignore("Remove to run test")
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@Test
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public void countAtSquare3() {
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BigInteger result = grains.computeNumberOfGrainsOnSquare(3);
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assertEquals(new BigInteger("4"), result);
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}
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@Ignore("Remove to run test")
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@Test
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public void countAtSquare4() {
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BigInteger result = grains.computeNumberOfGrainsOnSquare(4);
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assertEquals(new BigInteger("8"), result);
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}
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@Ignore("Remove to run test")
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@Test
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public void countAtSquare16() {
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BigInteger result = grains.computeNumberOfGrainsOnSquare(16);
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assertEquals(new BigInteger("32768"), result);
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}
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@Ignore("Remove to run test")
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@Test
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public void countAtSquare32() {
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BigInteger result = grains.computeNumberOfGrainsOnSquare(32);
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assertEquals(new BigInteger("2147483648"), result);
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}
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@Ignore("Remove to run test")
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@Test
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public void countAtSquare64() {
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BigInteger result = grains.computeNumberOfGrainsOnSquare(64);
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assertEquals(new BigInteger("9223372036854775808"), result);
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}
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@Ignore("Remove to run test")
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@Test
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public void errorOnNullBoardSize() {
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expectedException.expect(IllegalArgumentException.class);
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expectedException.expectMessage(wrongSquareMessage);
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grains.computeNumberOfGrainsOnSquare(0);
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}
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@Ignore("Remove to run test")
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@Test
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public void errorOnNegativeBoardSize() {
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expectedException.expect(IllegalArgumentException.class);
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expectedException.expectMessage(wrongSquareMessage);
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grains.computeNumberOfGrainsOnSquare(-1);
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}
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@Ignore("Remove to run test")
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@Test
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public void errorOnExcessiveBoardSize() {
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expectedException.expect(IllegalArgumentException.class);
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expectedException.expectMessage(wrongSquareMessage);
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grains.computeNumberOfGrainsOnSquare(65);
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}
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@Ignore("Remove to run test")
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@Test
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public void totalNumberOfGrainsOnABoard() {
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BigInteger total = grains.computeTotalNumberOfGrainsOnBoard();
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assertEquals(new BigInteger("18446744073709551615"), total);
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}
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}

‎exercises/settings.gradle‎

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include 'gigasecond'
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include 'go-counting'
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include 'grade-school'
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include 'grains'
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include 'grep'
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include 'hamming'
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include 'hexadecimal'

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