Block Sum

mediumnumpy_manipulation

Implement block_sum(X, b).

Given a 2D array X of shape (n, n) where n is divisible by b, return a (n//b, n//b) array whose entry (r, c) is the sum of the non-overlapping b x b block at block-row r, block-column c. Use reshaping — no for/while loops.

Constraints

no scipy, sklearn
no for/while loops

Your solution

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Hints

Hint 1

Reshape (n, n) to (n//b, b, n//b, b) and sum axes 1 and 3.