Suppose that we are given a list of non-zero integers $(a_1,...,a_n)$ and we want to decide whether there exist $(x_1,...,x_n)$ such that
$x_1a_1 + x_2a_2 + ... + x_na_n = 0$,
$x_i$ $\in$ $\{-1,0,1\}$, with at least one $x_i \neq$ 0.
Note that this is not the same as PARTITION, where the restriction $x_i \in \{-1,1\}$ would give a solution. Of course we should also be aware that with $x_i \in \{0,1\}$ is the NP complete problem SUBSET-SUM. I don't see any obvious way of reducing SUBSET-SUM or PARTITION to this problem. For example, attempting to reduce a 0-1 problem to $\{-1,0,1\}$ problem by appending the list with negative elements appears to accomplish nothing.
The closest problem that I found was described this post, calling the problem WEAK-PARTITION. However, the link that the original poster provided is currently broken.
I would like to know whether there is an efficient (i.e. polynomial time) algorithm known for this problem and whether anyone knows of further references to this problem.
