Variable Window Pattern

Variable-size windows grow and shrink based on a condition. The pattern is:

$1.$ Expand: move $right$ forward, adding the new element to the window.

$2.$ Shrink: while the window violates some constraint, move $left$ forward, removing elements.

$3.$ Update: after each expansion, update your answer. Here's the trick: each element is added once and removed at most once. Even though there's a nested loop, total work is $O(n)$.