diff --git a/src/main/java/com/thealgorithms/misc/MapReduce.java b/src/main/java/com/thealgorithms/misc/MapReduce.java index c076957344f9..d98b2ee2dd03 100644 --- a/src/main/java/com/thealgorithms/misc/MapReduce.java +++ b/src/main/java/com/thealgorithms/misc/MapReduce.java @@ -7,35 +7,34 @@ import java.util.function.Function; import java.util.stream.Collectors; -/* -* MapReduce is a programming model for processing and generating large data sets with a parallel, -distributed algorithm on a cluster. -* It has two main steps: the Map step, where the data is divided into smaller chunks and processed in parallel, -and the Reduce step, where the results from the Map step are combined to produce the final output. -* Wikipedia link : https://en.wikipedia.org/wiki/MapReduce -*/ - +/** + * MapReduce is a programming model for processing and generating large data sets + * using a parallel, distributed algorithm on a cluster. + * It consists of two main phases: + * - Map: the input data is split into smaller chunks and processed in parallel. + * - Reduce: the results from the Map phase are aggregated to produce the final output. + * + * See also: https://en.wikipedia.org/wiki/MapReduce + */ public final class MapReduce { + private MapReduce() { } - /* - *Counting all the words frequency within a sentence. - */ - public static String mapreduce(String sentence) { - List wordList = Arrays.stream(sentence.split(" ")).toList(); - // Map step - Map wordCounts = wordList.stream().collect(Collectors.groupingBy(Function.identity(), LinkedHashMap::new, Collectors.counting())); - - // Reduce step - StringBuilder result = new StringBuilder(); - wordCounts.forEach((word, count) -> result.append(word).append(": ").append(count).append(",")); + /** + * Counts the frequency of each word in a given sentence using a simple MapReduce-style approach. + * + * @param sentence the input sentence + * @return a string representing word frequencies in the format "word: count,word: count,..." + */ + public static String countWordFrequencies(String sentence) { + // Map phase: split the sentence into words + List words = Arrays.asList(sentence.trim().split("\\s+")); - // Removing the last ',' if it exists - if (!result.isEmpty()) { - result.setLength(result.length() - 1); - } + // Group and count occurrences of each word, maintain insertion order + Map wordCounts = words.stream().collect(Collectors.groupingBy(Function.identity(), LinkedHashMap::new, Collectors.counting())); - return result.toString(); + // Reduce phase: format the result + return wordCounts.entrySet().stream().map(entry -> entry.getKey() + ": " + entry.getValue()).collect(Collectors.joining(",")); } } diff --git a/src/test/java/com/thealgorithms/misc/MapReduceTest.java b/src/test/java/com/thealgorithms/misc/MapReduceTest.java index c79c40701cc1..748dd0a563cf 100644 --- a/src/test/java/com/thealgorithms/misc/MapReduceTest.java +++ b/src/test/java/com/thealgorithms/misc/MapReduceTest.java @@ -2,22 +2,14 @@ import static org.junit.jupiter.api.Assertions.assertEquals; -import org.junit.jupiter.api.Test; +import org.junit.jupiter.params.ParameterizedTest; +import org.junit.jupiter.params.provider.CsvSource; public class MapReduceTest { - @Test - public void testMapReduceWithSingleWordSentence() { - String oneWordSentence = "Hactober"; - String result = MapReduce.mapreduce(oneWordSentence); - - assertEquals("Hactober: 1", result); - } - - @Test - public void testMapReduceWithMultipleWordSentence() { - String multipleWordSentence = "I Love Love HactoberFest"; - String result = MapReduce.mapreduce(multipleWordSentence); - - assertEquals("I: 1,Love: 2,HactoberFest: 1", result); + @ParameterizedTest + @CsvSource({"'hello world', 'hello: 1,world: 1'", "'one one two', 'one: 2,two: 1'", "'a a a a', 'a: 4'", "' spaced out ', 'spaced: 1,out: 1'"}) + void testCountWordFrequencies(String input, String expected) { + String result = MapReduce.countWordFrequencies(input); + assertEquals(expected, result); } }