I was wondering if a variation of the bin packing problem where the 'size' of a bin is calculated as the product of item sizes in a bin instead of their sum is NP-hard. It seems like it must be, but I don't know how to prove it.

More formally, the problem is as follows:

Given a list of positive integer item sizes $a_1, a_2, ..., a_n$ and a positive integer $x$, find the smallest positive integer $k$ such that it is possible to partition the items into $k$ disjoint sets $S_1, S_2, ..., S_k$ such that the product of sizes in each $S_i$ is $\leq x$.


1 Answer 1


The bin packing problem is strongly NP-hard. That means that even if the sizes are given in unary, the problem is still NP-hard.

In your case, your product-bin packing is equivalent to sum-bin packing, using $\log a_i$ and $\log x$ as sizes, and it is still NP-hard.


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