Stacks, Queues and Monotonic Structures

The problem

Three questions, one family:

1. Is a string of brackets like ([]{}) correctly nested?
2. For each element, where is the next element to its right that is larger?
3. For every window of k consecutive elements, what is the maximum?

Each asks about the most recent unresolved item, or the best item in a moving range. A stack and a deque answer them in one pass.