Challenge: Variable Window Size

What if the window size varies? At position $i$, valid $j \in [l_i, r_i]$ where bounds depend on $i$. If $l_i$ is non-decreasing, the left side still slides right. Pop expired elements from front as usual.

If $r_i$ is non-decreasing, new elements can be added in order. Standard monotonic queue works. If bounds are arbitrary, monotonic queue doesn't directly apply. Consider segment trees or other structures.