Advent of Code 2023 Day 21

— Day 21: Step Counter —

The gardener elf wants to go for a walk.

Starting from the garden plot marked S on your map, how many garden plots could the Elf reach in exactly 64 steps?

with open('data-2023-21.txt', 'r') as f:
    inp = f.read().splitlines()

Maybe write an explanation of the solution approach here

# here's another python cell for good luck

Paste part two here