Stack 8
- Leetcode 0496. Next Greater Element I
- Leetcode 0589. N-ary Tree Preorder Traversal
- Leetcode 0145. Binary Tree Postorder Traversal
- Leetcode 0144. Binary Tree Preorder Traversal
- Leetcode 0094. Binary Tree Inorder Traversal
- Leetcode 0232. Implement Queue using Stacks
- Leetcode 0155. Min Stack
- Leetcode 0020. Valid Parentheses