#Stack

Validate a custom expression containing '{', '}', and '*' where '*' can act as '{', '}', or empty. Check if it is balanced.

Solve a medium level problem related to stack for matching parentheses. Provide an algorithm and analyze the time complexity.

Implement a Min Stack that includes the ability to retrieve the minimum element in O(1) time. The stack should support standard stack operations: push, pop, and top.