Stacks, Queues, and Deques

Implement a stack using both an array and a linked list.

Solve the balanced parentheses problem using a stack.

Solve the 'next greater element' problem using a monotonic stack.

Implement a queue using both a circular array and a linked list.

Implement a queue using two stacks and analyze its amortized time complexity.

Implement a deque using a doubly linked list.

Solve the 'sliding window maximum' problem efficiently using a deque.

Convert an infix expression to postfix and evaluate it using a stack.