344. Add Reverse String Problem

algorithms-and-data-structures/src/main/java/com/xtenzq/arrays/TwoPointers.java

@@ -110,5 +110,24 @@ public static boolean isSubsequence(String s, String t) {
 
         return i == s.length();
     }
+
+    /**
+     * Reverses the input array of characters in-place.
+     *
+     * @param s the array of characters to be reversed
+     * @implNote This method runs in {@code O(n)} time complexity and {@code O(1)} space complexity,
+     * where {@code n} is the length of {@code s}.
+     * @see <a href="https://leetcode.com/problems/reverse-string/">344. Reverse String</a>
+     */
+    public static void reverseString(char[] s) {
+        int i = 0, j = s.length - 1;
+        while (i < j) {
+            var temp = s[i];
+            s[i] = s[j];
+            s[j] = temp;
+            i++;
+            j--;
+        }
+    }
 }
 

algorithms-and-data-structures/src/test/java/com/xtenzq/arrays/TwoPointersTest.java

@@ -6,6 +6,7 @@
 import static com.xtenzq.arrays.TwoPointers.canBeSummed;
 import static com.xtenzq.arrays.TwoPointers.isPalindrome;
 import static com.xtenzq.arrays.TwoPointers.mergeSortedArrays;
+import static com.xtenzq.arrays.TwoPointers.reverseString;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -281,4 +282,52 @@ void testInterleavedNonSubsequence() {
         String t = "abcde";
         assertFalse(isSubsequence(s, t));
     }
+
+    @Test
+    void testReverseStringWithEvenNumberOfCharacters() {
+        char[] input = {'h', 'e', 'l', 'l', 'o'};
+        char[] expected = {'o', 'l', 'l', 'e', 'h'};
+        reverseString(input);
+        assertArrayEquals(expected, input);
+    }
+
+    @Test
+    void testReverseStringWithOddNumberOfCharacters() {
+        char[] input = {'a', 'b', 'c', 'd', 'e'};
+        char[] expected = {'e', 'd', 'c', 'b', 'a'};
+        reverseString(input);
+        assertArrayEquals(expected, input);
+    }
+
+    @Test
+    void testReverseStringWithSingleCharacter() {
+        char[] input = {'a'};
+        char[] expected = {'a'};
+        reverseString(input);
+        assertArrayEquals(expected, input);
+    }
+
+    @Test
+    void testReverseStringWithEmptyArray() {
+        char[] input = {};
+        char[] expected = {};
+        reverseString(input);
+        assertArrayEquals(expected, input);
+    }
+
+    @Test
+    void testReverseStringWithRepeatedCharacters() {
+        char[] input = {'a', 'a', 'a', 'a'};
+        char[] expected = {'a', 'a', 'a', 'a'};
+        reverseString(input);
+        assertArrayEquals(expected, input);
+    }
+
+    @Test
+    void testReverseStringWithSpecialCharacters() {
+        char[] input = {'!', '@', '#', '$', '%'};
+        char[] expected = {'%', '$', '#', '@', '!'};
+        reverseString(input);
+        assertArrayEquals(expected, input);
+    }
 }