iterative deepening

    A graph search algorithm that will find the
   shortest path with some given property, even when the graph
   contains cycles.  When searching for a path through a graph,
   starting at a given initial node, where the path (or its end
   node) has some desired property, a depth-first search may
   never find a solution if it enters a cycle in the graph.
   Rather than avoiding cycles (i.e. never extend a path with a
   node it already contains), iterative deepening explores all
   paths up to length (or "depth") N, starting from N=0 and
   increasing N until a solution is found.

   (2004-01-26)