Add Minimum Window Substring algorithm in Sliding Window package (#6553)

* Create MinimumWindowSubstring.java

* Create MinimumWindowSubstringTest.java

* correct MinimumWindowSubstringTest.java

* Added more test cases

* Update MinimumWindowSubstringTest.java

* Update MinimumWindowSubstringTest.java

* Update MinimumWindowSubstringTest.java

* Update MinimumWindowSubstringTest.java

* Update MinimumWindowSubstringTest.java

* Update MinimumWindowSubstringTest.java

* Added test case "AAABBC" "AABC"

---------

Co-authored-by: Deniz Altunkapan <93663085+DenizAltunkapan@users.noreply.github.com>

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

@@ -0,0 +1,35 @@
+package com.thealgorithms.slidingwindow;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Finds the minimum window substring in {@code s} that contains all characters of {@code t}.
+ *
+ * @param s The input string to search within
+ * @param t The string with required characters
+ * @return The minimum window substring, or empty string if not found
+ * @author  (https://github.com/Chiefpatwal)
+ */
+public class MinimumWindowSubstringTest {
+
+    /**
+     * Tests for MinimumWindowSubstring.minWindow.
+     */
+    @Test
+    public void testMinimumWindowSubstring() {
+        assertEquals("BANC", MinimumWindowSubstring.minWindow("ADOBECODEBANC", "ABC"));
+        assertEquals("a", MinimumWindowSubstring.minWindow("a", "a"));
+        assertEquals("", MinimumWindowSubstring.minWindow("a", "aa"));
+        assertEquals("", MinimumWindowSubstring.minWindow("ADOBECODEBANC", "XYZ"));
+        assertEquals("BC", MinimumWindowSubstring.minWindow("ABCDEF", "BC"));
+        assertEquals("q", MinimumWindowSubstring.minWindow("abcdefghijklmnopqrstuvwxyz", "q"));
+        assertEquals("", MinimumWindowSubstring.minWindow("zzzzzzzzz", "zzzzzzzzzz"));
+        assertEquals("abbbbbcdd", MinimumWindowSubstring.minWindow("aaaaaaaaaaaabbbbbcdd", "abcdd"));
+        assertEquals("ABCDEFG", MinimumWindowSubstring.minWindow("ABCDEFG", "ABCDEFG"));
+        assertEquals("", MinimumWindowSubstring.minWindow("abc", "A"));
+        assertEquals("A", MinimumWindowSubstring.minWindow("aAbBcC", "A"));
+        assertEquals("AABBC", MinimumWindowSubstring.minWindow("AAABBC", "AABC"));
+    }
+}