Add SecondMinMax

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

@@ -0,0 +1,48 @@
+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 empty or length 1 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) {
+        int secMin = Integer.MAX_VALUE, min = Integer.MAX_VALUE;
+        checkInput(arr);
+        for (final int num : arr)
+            if (num < min) {
+                secMin = min;
+                min = num;
+            } else if ((num < secMin) && (num != min))
+                secMin = num;
+        if (secMin == Integer.MAX_VALUE) throw new IllegalArgumentException("Cant find Second Maximum / Minimum in array full of same numbers");
+        return secMin;
+    }
+
+    public static int findSecondMax(final int[] arr) {
+        int secMax = Integer.MIN_VALUE, max = Integer.MIN_VALUE;
+        checkInput(arr);
+        for (final int num : arr)
+            if (num > max) {
+                secMax = max;
+                max = num;
+            } else if ((num > secMax) && (num != max))
+                secMax = num;
+        if (secMax == Integer.MIN_VALUE) throw new IllegalArgumentException("Cant find Second Maximum / Minimum in array full of same numbers");
+        return secMax;
+    }
+
+    private static void checkInput(final int[] arr) {
+        if (arr.length == 0)
+            throw new IllegalArgumentException("Cant find Second Maximum / Minimum for empty array");
+        else if (arr.length == 1)
+            throw new IllegalArgumentException("Cant find Second Maximum / Minimum for single element");
+    }
+}

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

@@ -0,0 +1,39 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+public class SecondMinMaxTest {
+
+    private static final String EXP_MSG_ARR_IS_EMPTY = "Cant find Second Maximum / Minimum for empty array";
+    private static final String EXP_MSG_ARR_SINGLE_ELE = "Cant find Second Maximum / Minimum for single element";
+    private static final String EXP_MSG_ARR_SAME_ELE = "Cant find Second Maximum / Minimum in array full of same numbers";
+
+    @Test
+    public void testForEmptyInputArray() {
+        IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> SecondMinMax.findSecondMin(new int[] {}));
+        assertEquals(exception.getMessage(), EXP_MSG_ARR_IS_EMPTY);
+    }
+
+    @Test
+    public void testForArrayWithSingleElement() {
+        IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> SecondMinMax.findSecondMax(new int[] {1}));
+        assertEquals(exception.getMessage(), EXP_MSG_ARR_SINGLE_ELE);
+    }
+
+    @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);
+    }
+
+    @Test
+    public void testForValidOutput() {
+        assertEquals(2, SecondMinMax.findSecondMin(new int[] {1, 2}));
+        assertEquals(1, SecondMinMax.findSecondMax(new int[] {1, 2}));
+        assertEquals(2, SecondMinMax.findSecondMin(new int[] {10, 1, 2, 4, 6, 3, 5, 7, 3, 2, 5, 7, 4, 2, 1, 212, 343, 565, 2232, 65565}));
+        assertEquals(2232, SecondMinMax.findSecondMax(new int[] {10, 1, 2, 4, 6, 3, 5, 7, 3, 2, 5, 7, 4, 2, 1, 212, 343, 565, 2232, 65565}));
+    }
+}