One of my best commits was removing about 60K lines of code, a whole "server" (it was early 2000's) with that had to hold all of its state in memory and replacing them with about 5k of logic that was lightweight enough to piggyback into another service and had no in-memory state at all. That was pure a algorithmic win - figuring out that a specific guided subgraph isomorphism where the target was a tree (directed, non cyclic graph with a single root) was possible by a single walk through the origin (general) directed bi-graph while emitting vertices and edges to the output graph (tree) and maintaining only a small in-process peek-able stack of steps taken from the root that can affect the current generation step (not necessarily just parent path).
I still remember the behemoth of a commit that was "-60,000 (or similar) lines of code". Best commit I ever pushed.
Those were fun times. Hadn't done anything algorithmically impressive since.
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