son is done to check
if a match exists. The worst case time complexity of Rabin-Karp is `O(m *
n)` where `m ~ len(needle)` and `n ~ len(haystack)`. Its worst case space
complexity is constant.

The main utility of Rabin-Karp is that the searcher can be constructed very
quickly with very little memory. This makes it especially useful when searching
for small needles in small haystacks, as it might finish its search before a
beefier algorithm (like Two-Way) even starts.

[rabinkarp]: https://en.wikipedia.org/wiki/Rabin%E2%80%93Karp_algorithm