Sharon Curtis and Shin-Cheng Mu have a Functional Pearl using zygomorphisms to find maximally dense segments (a generalization of maximum segment sums). Zygomorphisms are seemingly a good fit for sliding window problems once you are accustomed to them.
http://www.iis.sinica.edu.tw/~scm/2010/functional-pearl-maximally-dense-segments/
I’d nominate the authors for extra credit as they’ve avoided the use of the fixed-point Mu functor.