Add Count Nice Subarrays sliding using window algorithm (#7206)

* Add Count Nice Subarrays sliding window algorithm

* Add detailed comments and reference to CountNiceSubarrays

* Fix clang-format issues in CountNiceSubarrays

* Added extra edge cases

* changes made

src/test/java/com/thealgorithms/slidingwindow/CountNiceSubarraysTest.java

@@ -0,0 +1,55 @@
+package com.thealgorithms.slidingwindow;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class CountNiceSubarraysTest {
+    @Test
+    void testExampleCase() {
+        int[] nums = {1, 1, 2, 1, 1};
+        assertEquals(2, CountNiceSubarrays.countNiceSubarrays(nums, 3));
+    }
+
+    @Test
+    void testAllEvenNumbers() {
+        int[] nums = {2, 4, 6, 8};
+        assertEquals(0, CountNiceSubarrays.countNiceSubarrays(nums, 1));
+    }
+
+    @Test
+    void testSingleOdd() {
+        int[] nums = {1};
+        assertEquals(1, CountNiceSubarrays.countNiceSubarrays(nums, 1));
+    }
+
+    @Test
+    void testMultipleChoices() {
+        int[] nums = {2, 2, 1, 2, 2, 1, 2};
+        assertEquals(6, CountNiceSubarrays.countNiceSubarrays(nums, 2));
+    }
+
+    @Test
+    void testTrailingEvenNumbers() {
+        int[] nums = {1, 2, 2, 2};
+        assertEquals(4, CountNiceSubarrays.countNiceSubarrays(nums, 1));
+    }
+
+    @Test
+    void testMultipleWindowShrinks() {
+        int[] nums = {1, 1, 1, 1};
+        assertEquals(3, CountNiceSubarrays.countNiceSubarrays(nums, 2));
+    }
+
+    @Test
+    void testEvensBetweenOdds() {
+        int[] nums = {2, 1, 2, 1, 2};
+        assertEquals(4, CountNiceSubarrays.countNiceSubarrays(nums, 2));
+    }
+
+    @Test
+    void testShrinkWithTrailingEvens() {
+        int[] nums = {2, 2, 1, 2, 2, 1, 2, 2};
+        assertEquals(9, CountNiceSubarrays.countNiceSubarrays(nums, 2));
+    }
+}