Practice: Queues and Deques

Four problems for queues and deques: a plain queue, round robin, a window of recent numbers, and a deque that keeps being reversed.

• Read a command as a string (or a char) first, then read its number only if the command has one.
• Round robin: keep pairs (job number, work left) in the queue, and the clock in a long long.
• For the first negative in every window, the queue holds positions, not values: then you can tell which ones have slid out of the window.
• For the reversible deque, keep a rev flag. While it is true, every command that names a side uses the other end.