  A new numerical method to calculate exact ground states of multi-fluxline
systems with quenched disorder is presented, which is based on the minimum cost
flow algorithm from combinatorial optimization. We discuss several models that
can be studied with this method including their specific implementations,
physically relevant observables and results: 1) the N-line model with N
fluxlines (or directed polymers) in a d-dimensional environment with point
and/or columnar disorder and hard or soft core repulsion; 2) the vortex glass
model for a disordered superconductor in the strong screening limit and 3) the
Sine-Gordon model with random pase shifts in the strong coupling limit.
