Update DIRECTORY.md

Author: DenizAltunkapan

DIRECTORY.md

@@ -268,6 +268,7 @@
             - 📄 [BinaryTree](src/main/java/com/thealgorithms/datastructures/trees/BinaryTree.java)
             - 📄 [BoundaryTraversal](src/main/java/com/thealgorithms/datastructures/trees/BoundaryTraversal.java)
             - 📄 [CeilInBinarySearchTree](src/main/java/com/thealgorithms/datastructures/trees/CeilInBinarySearchTree.java)
+            - 📄 [CentroidDecomposition](src/main/java/com/thealgorithms/datastructures/trees/CentroidDecomposition.java)
             - 📄 [CheckBinaryTreeIsValidBST](src/main/java/com/thealgorithms/datastructures/trees/CheckBinaryTreeIsValidBST.java)
             - 📄 [CheckIfBinaryTreeBalanced](src/main/java/com/thealgorithms/datastructures/trees/CheckIfBinaryTreeBalanced.java)
             - 📄 [CheckTreeIsSymmetric](src/main/java/com/thealgorithms/datastructures/trees/CheckTreeIsSymmetric.java)
@@ -785,6 +786,7 @@
           - 📄 [StackPostfixNotation](src/main/java/com/thealgorithms/stacks/StackPostfixNotation.java)
           - 📄 [StackUsingTwoQueues](src/main/java/com/thealgorithms/stacks/StackUsingTwoQueues.java)
           - 📄 [TrappingRainwater](src/main/java/com/thealgorithms/stacks/TrappingRainwater.java)
+          - 📄 [ValidParentheses](src/main/java/com/thealgorithms/stacks/ValidParentheses.java)
         - 📁 **strings**
           - 📄 [AhoCorasick](src/main/java/com/thealgorithms/strings/AhoCorasick.java)
           - 📄 [Alphabetical](src/main/java/com/thealgorithms/strings/Alphabetical.java)
@@ -1069,6 +1071,7 @@
             - 📄 [BinaryTreeTest](src/test/java/com/thealgorithms/datastructures/trees/BinaryTreeTest.java)
             - 📄 [BoundaryTraversalTest](src/test/java/com/thealgorithms/datastructures/trees/BoundaryTraversalTest.java)
             - 📄 [CeilInBinarySearchTreeTest](src/test/java/com/thealgorithms/datastructures/trees/CeilInBinarySearchTreeTest.java)
+            - 📄 [CentroidDecompositionTest](src/test/java/com/thealgorithms/datastructures/trees/CentroidDecompositionTest.java)
             - 📄 [CheckBinaryTreeIsValidBSTTest](src/test/java/com/thealgorithms/datastructures/trees/CheckBinaryTreeIsValidBSTTest.java)
             - 📄 [CheckIfBinaryTreeBalancedTest](src/test/java/com/thealgorithms/datastructures/trees/CheckIfBinaryTreeBalancedTest.java)
             - 📄 [CheckTreeIsSymmetricTest](src/test/java/com/thealgorithms/datastructures/trees/CheckTreeIsSymmetricTest.java)
@@ -1544,6 +1547,7 @@
           - 📄 [StackPostfixNotationTest](src/test/java/com/thealgorithms/stacks/StackPostfixNotationTest.java)
           - 📄 [StackUsingTwoQueuesTest](src/test/java/com/thealgorithms/stacks/StackUsingTwoQueuesTest.java)
           - 📄 [TrappingRainwaterTest](src/test/java/com/thealgorithms/stacks/TrappingRainwaterTest.java)
+          - 📄 [ValidParenthesesTest](src/test/java/com/thealgorithms/stacks/ValidParenthesesTest.java)
         - 📁 **strings**
           - 📄 [AhoCorasickTest](src/test/java/com/thealgorithms/strings/AhoCorasickTest.java)
           - 📄 [AlphabeticalTest](src/test/java/com/thealgorithms/strings/AlphabeticalTest.java)