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Merge pull request #302 from sir-gon/feature/frequency_queries
Feature/frequency queries
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‎algorithm-exercises-java/src/main/java/ae/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/FrequencyQueries.java

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package ae.hackerrank.interview_preparation_kit.dictionaries_and_hashmaps;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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/**
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* FrequencyQueries.
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*
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* @link Problem definition
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* [[docs/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/frequency-queries.md]]
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*/
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public class FrequencyQueries {
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private FrequencyQueries() {
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}
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private static final long __INITIAL__ = 1L;
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private static final int __INSERT__ = 1;
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private static final int __DELETE__ = 2;
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private static final int __SELECT__ = 3;
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private static final int __NOT_FOUND__ = 0;
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private static final int __FOUND__ = 1;
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Map<Long, Long> valueFreqs = new HashMap<>();
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Map<Long, List<Long>> freqMap = new HashMap<>();
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List<Integer> result = new ArrayList<>();
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void insert(Long value) {
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Long currentFreqCount = this.valueFreqs.getOrDefault(value, null);
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Long newFreqCount;
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List<Long> newFreq;
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newFreqCount = (currentFreqCount == null ? __INITIAL__ : currentFreqCount + 1L);
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valueFreqs.put(value, newFreqCount);
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newFreq = freqMap.getOrDefault(newFreqCount, null);
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// delete current frequency
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if (currentFreqCount != null) {
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freqMap.get(currentFreqCount).remove(value);
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if (freqMap.get(currentFreqCount).isEmpty()) {
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freqMap.remove(currentFreqCount);
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}
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}
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// add new frequency
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if (newFreq == null) {
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newFreq = new ArrayList<>();
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newFreq.add(value);
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freqMap.put(newFreqCount, newFreq);
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} else {
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freqMap.get(newFreqCount).add(value);
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}
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}
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void delete(Long value) {
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Long currentFreqCount = this.valueFreqs.getOrDefault(value, null);
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Long newFreqCount;
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List<Long> newFreq;
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newFreqCount = (currentFreqCount == null ? 0 : currentFreqCount - 1L);
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if (newFreqCount > 0L) {
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valueFreqs.put(value, newFreqCount);
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newFreq = freqMap.getOrDefault(newFreqCount, null);
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// add new frequency
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if (newFreq == null) {
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newFreq = new ArrayList<>();
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newFreq.add(value);
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freqMap.put(newFreqCount, newFreq);
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} else {
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freqMap.get(newFreqCount).add(value);
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}
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} else {
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valueFreqs.remove(value);
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}
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// delete current frequency
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if (currentFreqCount != null) {
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freqMap.get(currentFreqCount).remove(value);
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if (freqMap.get(currentFreqCount).isEmpty()) {
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freqMap.remove(currentFreqCount);
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}
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}
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}
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/**
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* FrequencyQueries.
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*/
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static List<Integer> freqQuery(List<List<Integer>> queries) {
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FrequencyQueries fq = new FrequencyQueries();
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fq.result = new ArrayList<>();
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for (List<Integer> query : queries) {
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int operation = query.get(0);
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long value = query.get(1);
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switch (operation) {
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case __INSERT__:
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fq.insert(value);
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break;
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case __DELETE__:
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fq.delete(value);
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break;
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case __SELECT__:
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fq.result.add(fq.freqMap.containsKey(value) ? __FOUND__ : __NOT_FOUND__);
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break;
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default:
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throw new IllegalArgumentException(
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"Operation %d not supported".formatted(operation));
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}
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}
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return fq.result;
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}
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}

‎algorithm-exercises-java/src/test/java/ae/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/FrequencyQueriesTest.java

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package ae.hackerrank.interview_preparation_kit.dictionaries_and_hashmaps;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import java.io.IOException;
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import java.util.List;
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import org.junit.jupiter.api.BeforeAll;
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import org.junit.jupiter.api.Test;
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import org.junit.jupiter.api.TestInstance;
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import org.junit.jupiter.api.TestInstance.Lifecycle;
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import util.JsonLoader;
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@TestInstance(Lifecycle.PER_CLASS)
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class FrequencyQueriesTest {
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public static class FrequencyQueriesTestCase {
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public String title;
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public List<List<Integer>> input;
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public List<Integer> expected;
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}
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List<FrequencyQueriesTestCase> testCases;
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List<FrequencyQueriesTestCase> testCase6;
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List<FrequencyQueriesTestCase> testCaseBorderCases;
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List<FrequencyQueriesTestCase> testCaseBorderCaseException;
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@BeforeAll
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void setup() throws IOException {
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String path;
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path = String.join("/",
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"hackerrank",
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"interview_preparation_kit",
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"dictionaries_and_hashmaps",
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"frequency_queries.testcases.json");
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this.testCases = JsonLoader.loadJson(path, FrequencyQueriesTestCase.class);
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path = String.join("/",
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"hackerrank",
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"interview_preparation_kit",
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"dictionaries_and_hashmaps",
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"frequency_queries.testcase6.json");
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this.testCase6 = JsonLoader.loadJson(path, FrequencyQueriesTestCase.class);
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path = String.join("/",
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"hackerrank",
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"interview_preparation_kit",
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"dictionaries_and_hashmaps",
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"frequency_queries.testcase_border_cases.json");
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this.testCaseBorderCases = JsonLoader.loadJson(path, FrequencyQueriesTestCase.class);
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path = String.join("/",
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"hackerrank",
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"interview_preparation_kit",
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"dictionaries_and_hashmaps",
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"frequency_queries.testcase_border_case_exception.json");
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this.testCaseBorderCaseException = JsonLoader.loadJson(path, FrequencyQueriesTestCase.class);
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}
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@Test
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void testFrequencyQueries() {
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List<Integer> solutionFound;
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for (FrequencyQueriesTestCase test : testCases) {
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solutionFound = FrequencyQueries.freqQuery(test.input);
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assertEquals(test.expected, solutionFound,
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"%s(%s) answer must be: %s".formatted(
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"FrequencyQueriesTest.freqQuery",
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test.input,
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test.expected));
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}
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}
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@Test
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void testFrequencyQueriesBigCases() {
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List<Integer> solutionFound;
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for (FrequencyQueriesTestCase test : testCase6) {
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solutionFound = FrequencyQueries.freqQuery(test.input);
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assertEquals(test.expected, solutionFound,
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"%s(%s) answer must be: %s".formatted(
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"FrequencyQueriesTest.freqQuery",
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test.input,
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test.expected));
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}
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}
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@Test
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void testFrequencyQueriesBorderCases() {
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List<Integer> solutionFound;
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for (FrequencyQueriesTestCase test : testCaseBorderCases) {
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solutionFound = FrequencyQueries.freqQuery(test.input);
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assertEquals(test.expected, solutionFound,
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"%s(%s) answer must be: %s".formatted(
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"FrequencyQueriesTest.freqQuery",
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test.input,
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test.expected));
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}
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}
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@Test
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void testFrequencyQueriesBorderCaseException() {
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for (FrequencyQueriesTestCase test : testCaseBorderCaseException) {
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Exception exception = assertThrows(IllegalArgumentException.class, () -> {
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FrequencyQueries.freqQuery(test.input);
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});
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String expectedMessage = "Operation 4 not supported";
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String actualMessage = exception.getMessage();
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assertTrue(actualMessage.contains(expectedMessage));
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}
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}
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}

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