first — making pop O(1) but push O(n). - (The reverse tradeoff — O(1) push, O(n) pop by reversing only on pop when a second stack is empty — is the more common two-stack queue variant, but this file ...
The application presents a top-level menu where you pick a data structure, then a sub-menu with every operation that structure supports. Each structure lives in its own header/implementation pair, so ...