1. Implement a stack with a maximum size limit and handle overflow.
2. Write a function to evaluate a complex expression with multiple operators using a stack.
3. Implement a function to sort a stack using recursion without using additional data structures.
4. Write a function to find the next greater element for each element in a stack.
5. Implement a function to convert infix expressions to prefix expressions using a stack.
6. Write a function to check if a given sequence of operations (push/pop) on a stack is valid.
7. Implement a stack that supports multiple data types, including integers, strings, and objects.
8. Write a function to reverse the elements of a stack using a temporary stack.
9. Implement a function to find the longest balanced substring of parentheses using a stack.
10. Write a function to check if a stack is a permutation of another stack.
11. Implement a function to find the middle element of a stack in O(1) time.
12. Write a function to implement a stack that returns the maximum element in O(1) time.
13. Implement a function to create a min stack that supports push, pop, and retrieving the minimum element.
14. Write a function to find the intersection of two stacks without using additional memory.
15. Implement a function to remove duplicates from a stack while maintaining the order of elements.
16. Write a function to implement a stack that supports a getRandom operation in O(1) time.
17. Implement a function to simulate a queue using two stacks.
18. Write a function to check if two stacks can produce the same sequence of elements.
19. Implement a function to generate all valid combinations of parentheses using a stack.
20. Write a function to evaluate a prefix expression using a stack.
21. Implement a function to find the sum of elements in a stack without using additional space.
22. Write a function to determine if a stack is a subsequence of another stack.
23. Implement a function to find the largest rectangle area in a histogram represented by a stack.
24. Write a function to implement a stack-based DFS for a graph traversal.
25. Implement a function to perform a depth-first search on a binary tree using a stack.
26. Write a function to implement a stack that returns the second minimum element efficiently.
27. Implement a function to find the first non-repeating character in a string using a stack.
28. Write a function to check if a stack can be sorted using another stack.
29. Implement a function to calculate the height of a binary tree using a stack.
30. Write a function to generate all subsets of a set using a stack.
31. Implement a function to find the longest valid parentheses substring using a stack.
32. Write a function to implement a stack-based calculator for basic arithmetic operations.
33. Implement a function to find the shortest valid parentheses substring using a stack.
34. Write a function to create a stack that maintains the order of elements based on a custom comparator.
35. Implement a function to find the kth largest element in a stack using a temporary stack.
36. Write a function to implement a stack that allows inserting elements at the bottom.
37. Implement a function to sort a stack in ascending order using another stack.
38. Write a function to find pairs of elements in a stack that sum to a target value.
39. Implement a function to merge two sorted stacks into one sorted stack.
40. Write a function to convert a postfix expression to an infix expression using a stack.