Consider the following decision problem:

Given $([b_1, \cdots, b_n],t)$, where $[b_1, \cdots b_n]$ is an array of natural numbers each less than $n^c$ and $t$ is a target natural number, do there exist natural numbers $f_1, \cdots f_n$ such that

  1. $f_i \le b_i$ for all $1 \le i \le n$
  2. $\prod_{i=1}^{n} f_i = t$?

We guess that if the prime factorization of the target $t$ is given, then the problem might be polynomial, and in general, it seems similar to subset-product and might be NP-complete, but we couldn't prove an exact result or find a reference.

Are there any references/results for time complexity of this problem (in the case where the prime factorization of $t$ is given and when it isn't)? If an unpublished solution exists, we'd appreciate a hint!

  • $\begingroup$ I think it is unlikely that the problem is in P if the factorization of $t$ is given but NP-complete if the factorization is not given, as factoring is considered unlikely to be NP-complete. $\endgroup$
    – D.W.
    Dec 11, 2023 at 0:05
  • $\begingroup$ Since each number $b_i$ is less than $n^c$ and the input size is proportional to $n$, using a naive prime factorization algorithm for $t$, keeps the running time polynomial. So, it is safe to assume that prime factorization is given for $t$. $\endgroup$ Dec 11, 2023 at 9:44


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