Add SecondMinMax

src/main/java/com/thealgorithms/maths/SecondMinMax.java

@@ -0,0 +1,50 @@
+package com.thealgorithms.maths;
+
+public final class SecondMinMax {
+
+    /**
+     * @brief Finds the Second minimum / maximum value from the array
+     * @param int array
+     * @exception IllegalArgumentException => if input array is of length less than 2 also if all elements are same
+     * @return the second minimum / maximum value from the input array
+     * @author Bharath Sanjeevi ( https://github.com/BharathSanjeeviT )
+     */
+
+    private SecondMinMax() {
+    }
+
+    public static int findSecondMin(final int[] arr) {
+        checkInput(arr);
+        int secMin = Integer.MAX_VALUE, min = Integer.MAX_VALUE;
+        for (final int num : arr)
+            if (num < min) {
+                secMin = min;
+                min = num;
+            } else if ((num < secMin) && (num != min)) {
+                secMin = num;
+            }
+        return checkOutput(secMin);
+    }
+
+    public static int findSecondMax(final int[] arr) {
+        checkInput(arr);
+        int secMax = Integer.MIN_VALUE, max = Integer.MIN_VALUE;
+        for (final int num : arr)
+            if (num > max) {
+                secMax = max;
+                max = num;
+            } else if ((num > secMax) && (num != max)) {
+                secMax = num;
+            }
+        return checkOutput(secMax);
+    }
+
+    private static void checkInput(final int[] arr) {
+        if (arr.length < 2) throw new IllegalArgumentException("Input array must have length of at least two");
+    }
+
+    private static int checkOutput(final int secNum) {
+        if ((secNum == Integer.MAX_VALUE) || (secNum == Integer.MIN_VALUE)) throw new IllegalArgumentException("Input array should have at least 2 distinct elements");
+        return secNum;
+    }
+}

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

@@ -0,0 +1,55 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+public class SecondMinMaxTest {
+
+    private static final String EXP_MSG_ARR_LEN_LESS_2 = "Input array must have length of at least two";
+    private static final String EXP_MSG_ARR_SAME_ELE = "Input array should have at least 2 distinct elements";
+
+    @Test
+    public void testForEmptyInputArray() {
+        IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> SecondMinMax.findSecondMin(new int[] {}));
+        assertEquals(exception.getMessage(), EXP_MSG_ARR_LEN_LESS_2);
+    }
+
+    @Test
+    public void testForArrayWithSingleElement() {
+        IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> SecondMinMax.findSecondMax(new int[] {1}));
+        assertEquals(exception.getMessage(), EXP_MSG_ARR_LEN_LESS_2);
+    }
+
+    @Test
+    public void testForArrayWithSameElements() {
+        IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> SecondMinMax.findSecondMin(new int[] {1, 1, 1, 1}));
+        assertEquals(exception.getMessage(), EXP_MSG_ARR_SAME_ELE);
+    }
+
+    @ParameterizedTest
+    @MethodSource("inputStreamMin")
+    void numberTestsMin(int expected, int[] input) {
+        Assertions.assertEquals(expected, SecondMinMax.findSecondMin(input));
+    }
+
+    private static Stream<Arguments> inputStreamMin() {
+        return Stream.of(Arguments.of(2, new int[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}), Arguments.of(5, new int[] {5, 4, 5, 5, 5}), Arguments.of(0, new int[] {-1, 0}), Arguments.of(-9, new int[] {-10, -9, -8, -7, -6, -5, -4, -3, -2, -1}), Arguments.of(-2, new int[] {3, -2, 3, 9, -4, -4, 8}));
+    }
+
+    @ParameterizedTest
+    @MethodSource("inputStreamMax")
+    void numberTestsMax(int expected, int[] input) {
+        Assertions.assertEquals(expected, SecondMinMax.findSecondMax(input));
+    }
+
+    private static Stream<Arguments> inputStreamMax() {
+        return Stream.of(Arguments.of(9, new int[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}), Arguments.of(4, new int[] {5, 5, 4, 5, 5}), Arguments.of(-1, new int[] {-1, 0}), Arguments.of(-2, new int[] {-10, -9, -8, -7, -6, -5, -4, -3, -2, -1}), Arguments.of(8, new int[] {3, -2, 3, 9, -4, -4, 8}));
+    }
+}