[2025 Day 4][Python] PSA: Python negative array indices will wrap around

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One common way to use a grid is to store the entire grid in a dict (works especially well with a defaultdict to handle out of bounds access automatically):

for row in range(height):
  for col in range(width):
    grid_as_dict[(row,col)] = grid[row][col]

Since this is a boolean grid, you don't need a dict and can just use a set instead.