2D Array / Matrix Processing

Row/column sums, prefix on grids, four directions scan.

Try this in Python

m = [[1, 2], [3, 4]]
print([sum(row) for row in m])

Key takeaways

• Index checks on neighbors: deltas [(1,0),(-1,0),(0,1),(0,-1)].
• Rotate matrix via transpose + reverse rows.
• Memory traversal order for cache—rare in Python contests.