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BharathSanjeeviTvil02
BharathSanjeeviT
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vil02
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Add SecondMinMax (TheAlgorithms#4432)
* Added Second Min/Max program * Clang-format-lint error resolved * Clang-format-error 2 * Added Program to find Second Minimum/Maximum element * Test File & few changes * Clang-lint-error resolved * Maven Build Error Resolved * Clang-lint-error resolved * Clang-lint-error resolved 2 * Changes Resolved * Test Arguements are Streamed * Clang-lint-error resolved * incresed code reusability * Added Program to find Second Min / Max * Program to find Second Min / Max * Program to find Second Minimum / Maximum * Program to find Second Best Number * style: mark `initialVal` as `final` * style: resolve `MultipleVariableDeclarations` Each variable declaration must be in its own statement. --------- Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>
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‎src/main/java/com/thealgorithms/maths/SecondMinMax.java‎

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package com.thealgorithms.maths;
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import java.util.function.BiPredicate;
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public final class SecondMinMax {
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/**
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* Utility class for finding second maximum or minimum based on BiPredicate
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* @exception IllegalArgumentException => if input array is of length less than 2 also if all elements are same
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* @return the second minimum / maximum value from the input array
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* @author Bharath Sanjeevi ( https://github.com/BharathSanjeeviT )
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*/
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private SecondMinMax() {
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}
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private static int secondBest(final int[] arr, final int initialVal, final BiPredicate<Integer, Integer> isBetter) {
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checkInput(arr);
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int best = initialVal;
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int secBest = initialVal;
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for (final int num : arr) {
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if (isBetter.test(num, best)) {
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secBest = best;
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best = num;
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} else if ((isBetter.test(num, secBest)) && (num != best)) {
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secBest = num;
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}
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}
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checkOutput(secBest, initialVal);
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return secBest;
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}
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/**
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* @brief Finds the Second minimum / maximum value from the array
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* @param arr the input array
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* @exception IllegalArgumentException => if input array is of length less than 2 also if all elements are same
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* @return the second minimum / maximum value from the input array
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* @author Bharath Sanjeevi ( https://github.com/BharathSanjeeviT )
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*/
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public static int findSecondMin(final int[] arr) {
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return secondBest(arr, Integer.MAX_VALUE, (a, b) -> a < b);
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}
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public static int findSecondMax(final int[] arr) {
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return secondBest(arr, Integer.MIN_VALUE, (a, b) -> a > b);
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}
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private static void checkInput(final int[] arr) {
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if (arr.length < 2) {
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throw new IllegalArgumentException("Input array must have length of at least two");
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}
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}
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private static void checkOutput(final int secNum, final int initialVal) {
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if (secNum == initialVal) {
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throw new IllegalArgumentException("Input array should have at least 2 distinct elements");
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}
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}
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}

‎src/test/java/com/thealgorithms/maths/SecondMinMaxTest.java‎

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package com.thealgorithms.maths;
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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 java.util.stream.Stream;
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import org.junit.jupiter.api.Assertions;
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import org.junit.jupiter.api.Test;
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import org.junit.jupiter.params.ParameterizedTest;
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import org.junit.jupiter.params.provider.Arguments;
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import org.junit.jupiter.params.provider.MethodSource;
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public class SecondMinMaxTest {
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private static final String EXP_MSG_ARR_LEN_LESS_2 = "Input array must have length of at least two";
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private static final String EXP_MSG_ARR_SAME_ELE = "Input array should have at least 2 distinct elements";
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public static class TestCase {
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public TestCase(final int[] inInputArray, final int inSecondMin, final int inSecondMax) {
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inputArray = inInputArray;
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secondMin = inSecondMin;
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secondMax = inSecondMax;
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}
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final int[] inputArray;
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final int secondMin;
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final int secondMax;
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}
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@Test
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public void testForEmptyInputArray() {
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IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> SecondMinMax.findSecondMin(new int[] {}));
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assertEquals(exception.getMessage(), EXP_MSG_ARR_LEN_LESS_2);
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}
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@Test
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public void testForArrayWithSingleElement() {
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IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> SecondMinMax.findSecondMax(new int[] {1}));
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assertEquals(exception.getMessage(), EXP_MSG_ARR_LEN_LESS_2);
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}
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@Test
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public void testForArrayWithSameElements() {
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IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> SecondMinMax.findSecondMin(new int[] {1, 1, 1, 1}));
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assertEquals(exception.getMessage(), EXP_MSG_ARR_SAME_ELE);
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}
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@ParameterizedTest
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@MethodSource("inputStream")
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void numberTests(final TestCase tc) {
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Assertions.assertEquals(tc.secondMax, SecondMinMax.findSecondMax(tc.inputArray));
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Assertions.assertEquals(tc.secondMin, SecondMinMax.findSecondMin(tc.inputArray));
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}
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private static Stream<Arguments> inputStream() {
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return Stream.of(Arguments.of(new TestCase(new int[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 2, 9)), Arguments.of(new TestCase(new int[] {5, 4, 5, 5, 5}, 5, 4)), Arguments.of(new TestCase(new int[] {-1, 0}, 0, -1)),
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Arguments.of(new TestCase(new int[] {-10, -9, -8, -7, -6, -5, -4, -3, -2, -1}, -9, -2)), Arguments.of(new TestCase(new int[] {3, -2, 3, 9, -4, -4, 8}, -2, 8)));
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}
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}

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