Day 7 was pretty tough, I initially ended up implementing an exponential in both time and memory solution that I killed because it was eating all the resources on my Mac Studio, and this poor little machine only has 32GB of memory (I stopped it at 118GB of memory, swapping badly!), This is what I ended up doing before/after:

• Before: Time O(2^k · L), memory O(2^k), where k is the number of splitters along a reachable path and L is path length. Exponential in k.
  
• After: Time O(R·C) (or O(R·C + s) with s split events), memory O©, where R = rows, C = columns. Polynomial/linear in grid size.