  Nature often builds physical structures tailored for specific information
processing tasks with computations encoded using diverse phenomena. These can
sometimes outperform typical general-purpose computers. However, describing the
construction and function of these unconventional computers is often
challenging. Here, we address this by introducing constructor algorithms in the
context of a robotic wire machine that can be programmed to build networks of
connected wires in response to a problem and then act upon these to efficiently
carry out a desired computation. We show how this approach can be used to solve
the NP-complete Subset Sum Problem (SSP) and provide information about the
number of solutions through changes in the voltages and currents measured
across these networks. This work provides a foundation for building
unconventional computers that encode information purely in the lengths and
connections of electrically conductive wires. It also demonstrates the power of
computing paradigms beyond digital logic and opens avenues to more fully
harness the inherent computational capabilities of diverse physical, chemical
and biological substrates.
