Scatter-Add by Index

mediumnumpy_reductions

Implement accumulate_at(values, idx, n).

Given 1D arrays values and idx (same length, idx values in [0, n)), return an array out of length n where out[k] is the sum of all values[j] for which idx[j] == k. No for/while loops.

Constraints

no scipy, sklearn
no for/while loops

Your solution

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Hints

Hint 1

np.bincount(idx, weights=values, minlength=n) sums values into bins by index.