feat-Add MaximumProductSubarray (#6711)

* feat-Add MaximumProductSubarray

* feat-changes

* fix: correct MaximumProductSubarray compilation errors

* fix-lints

* fix: apply clang-format to MaximumProductSubarrayTest.java

* fix: prevent integer overflow in MaximumProductSubarray using long type

src/test/java/com/thealgorithms/dynamicprogramming/MaximumProductSubarrayTest.java

@@ -0,0 +1,152 @@
+package com.thealgorithms.dynamicprogramming;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class MaximumProductSubarrayTest {
+
+    /**
+     * Test case for an array with all positive numbers.
+     * The expected maximum product is the product of all elements.
+     */
+    @Test
+    void testAllPositiveNumbers() {
+        int[] nums = {2, 3, 4};
+        int expected = 24;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be 24.");
+    }
+
+    /**
+     * Test case for an array with positive and negative numbers.
+     * The expected maximum product is 24 (subarray [2, -3, -4]).
+     */
+    @Test
+    void testMixedPositiveAndNegative() {
+        int[] nums = {2, -3, -4, 1};
+        int expected = 24;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be 24.");
+    }
+
+    /**
+     * Test case for an array containing zeros.
+     * The expected maximum product is 24 (subarray [4, 6]).
+     */
+    @Test
+    void testArrayWithZeros() {
+        int[] nums = {2, 3, 0, 4, 6};
+        int expected = 24;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be 24.");
+    }
+
+    /**
+     * Test case for an array with a single element.
+     * The expected maximum product is the element itself.
+     */
+    @Test
+    void testSingleElement() {
+        int[] nums = {5};
+        int expected = 5;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be 5.");
+    }
+
+    /**
+     * Test case for an array with all negative numbers.
+     * The expected maximum product is 12 (subarray [-3, -4]).
+     */
+    @Test
+    void testAllNegativeNumbers() {
+        int[] nums = {-2, -3, -4};
+        int expected = 12;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be 12.");
+    }
+
+    /**
+     * Test case for an array with negative numbers where odd count of negatives
+     * breaks the chain. The expected maximum product is 60 (subarray [-2, -3, 10]).
+     */
+    @Test
+    void testOddNegativeNumbers() {
+        int[] nums = {-2, -3, 10, -1};
+        int expected = 60;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be 60.");
+    }
+
+    /**
+     * Test case for an empty array.
+     * The expected maximum product is 0.
+     */
+    @Test
+    void testEmptyArray() {
+        int[] nums = {};
+        int expected = 0;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be 0 for an empty array.");
+    }
+
+    /**
+     * Test case for a null array.
+     * The expected maximum product is 0.
+     */
+    @Test
+    void testNullArray() {
+        int[] nums = null;
+        int expected = 0;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be 0 for a null array.");
+    }
+
+    /**
+     * Test case for an array with alternating positive and negative numbers.
+     * The expected maximum product is 6 (subarray [2, 3]).
+     */
+    @Test
+    void testAlternatingNumbers() {
+        int[] nums = {2, 3, -2, 4};
+        int expected = 6;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be 6.");
+    }
+
+    /**
+     * Test case for an array with large positive and negative numbers.
+     * The expected maximum product is 360 (subarray [6, -3, -20]).
+     */
+    @Test
+    void testLargeNumbers() {
+        int[] nums = {6, -3, -20, 0, 5};
+        int expected = 360;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be 360.");
+    }
+
+    /**
+     * Test case for an array with single negative number.
+     * The expected maximum product is the negative number itself.
+     */
+    @Test
+    void testSingleNegativeElement() {
+        int[] nums = {-8};
+        int expected = -8;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be -8.");
+    }
+
+    /**
+     * Test case for an array with multiple zeros.
+     * The expected maximum product is 6 (subarray [2, 3]).
+     */
+    @Test
+    void testMultipleZeros() {
+        int[] nums = {0, 2, 3, 0, 4};
+        int expected = 6;
+        int actual = MaximumProductSubarray.maxProduct(nums);
+        assertEquals(expected, actual, "The maximum product should be 6.");
+    }
+}