1. Stack Implementation: Implement a stack using an array.

2. Stack using Linked List: Implement a stack using a linked list.

3. Balanced Parentheses: Write a function to check if a string has balanced parentheses using a stack.

4. Reverse String: Use a stack to reverse a string.

5. Evaluate Postfix Expression: Implement a function to evaluate a postfix expression using a stack.

6. Sort Stack: Write a function to sort a stack.

7. Next Greater Element: Implement a function to find the next greater element for each element in an array using a stack.

8. Next Smaller Element: Write a function to find the next smaller element for each element in an array using a stack.

9. Stock Span Problem: Implement a function to solve the stock span problem using a stack.

10. Minimum Element in Stack: Design a stack that supports push, pop, and retrieving the minimum element in constant time.

11. Infix to Postfix Conversion: Write a function to convert an infix expression to a postfix expression using a stack.

12. Infix to Prefix Conversion: Implement a function to convert an infix expression to a prefix expression using a stack.

13. Postfix to Infix Conversion: Write a function to convert a postfix expression to an infix expression using a stack.

14. Prefix to Infix Conversion: Implement a function to convert a prefix expression to an infix expression using a stack.

15. Duplicate Parentheses: Write a function to check for duplicate parentheses in an expression using a stack.

16. Stack with Get Middle Operation: Design a stack with a function to get the middle element of the stack.

17. Valid Parentheses: Write a function to check if a string contains valid parentheses using a stack.

18. Celebrity Problem: Implement the celebrity problem using a stack.

19. Check for Redundant Brackets: Write a function to check for redundant brackets in an expression using a stack.

20. Decode String: Implement a function to decode a given encoded string using a stack.

21. Histogram Area: Write a function to find the largest rectangular area in a histogram using a stack.

22. Implement Queue using Stacks: Implement a queue using two stacks.

23. Check Palindrome: Use a stack to check if a given string is a palindrome.

24. Reverse Stack: Write a function to reverse a stack.

25. Sort Stack Recursively: Implement a function to sort a stack recursively.

26. Merge Intervals: Write a function to merge overlapping intervals using a stack.

27. Check Stack Permutations: Implement a function to check if two stacks' sequences are permutations of each other.

28. Basic Calculator: Write a function to implement a basic calculator that can evaluate simple expressions using a stack.

29. Largest Rectangle in Histogram: Implement a function to find the largest rectangle in a histogram using a stack.

30. Balanced Brackets: Write a function to check if a string has balanced brackets using a stack.