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Merged
merged 6 commits into from
Oct 25, 2023
Merged

Added MapReduce Algorithm in Misc Folder. #4828

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ca9d8b2
Added MapReduce Algorithm in Misc Folder.
aakiliqbal Oct 17, 2023
e6fcc14
Did formatting correctly
aakiliqbal Oct 17, 2023
9a51b56
Merge branch 'master' into master
aakiliqbal Oct 20, 2023
0190a73
Removed main function and added MapReduceTest
aakiliqbal Oct 22, 2023
7890e11
format the code
aakiliqbal Oct 22, 2023
96e1619
Merge branch 'master' into master
aakiliqbal Oct 24, 2023
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39 changes: 39 additions & 0 deletions src/main/java/com/thealgorithms/misc/MapReduce.java
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package com.thealgorithms.misc;

import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
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
*/

public class MapReduce {
/*
*Counting all the words frequency within a sentence.
*/
public static String mapreduce(String sentence) {
List<String> wordList = Arrays.stream(sentence.split(" ")).toList();

// Map step
Map<String, Long> 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(","));

// Removing the last ',' if it exists
if (!result.isEmpty()) {
result.setLength(result.length() - 1);
}

return result.toString();
}
}
23 changes: 23 additions & 0 deletions src/test/java/com/thealgorithms/misc/MapReduceTest.java
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package com.thealgorithms.misc;

import static org.junit.jupiter.api.Assertions.*;

import org.junit.jupiter.api.Test;

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);
}
}