Hmm -- assumed time complexity for well-built hash functions for get / put operations is O(1), is it not? Sure, absolute worst-case means every operation is going to collide. Hash functions themselves are O(1)... I'm not sure what you mean by "implicit factor of D"? Like hashing is going inflate the runtime by a small factor basically equivalent to the edit distance in Myers' approach?

I've been looking through a little bit more literature and it's clear to me that my implementation as it stands is not equipped to solve the Longest Common Substring problem [0]. Right now it's too greedy. I think with a tweak it could.

I think I'm mostly just surprised because when I sat down at my computer today, I had the impression that diffing was a "hard problem" -- to be able to implement something that (apparently) works in a short timeframe made me feel as though I did something wrong. (I have this code running in a staging environment now with a code editor, and it seems to be working smoothly and as expected.)

[0] https://en.wikipedia.org/wiki/Longest_common_substring_probl...