V Qc@sBdZdZdddYZdZedkr>endS(sN queens problem. The (well-known) problem is due to Niklaus Wirth. This solution is inspired by Dijkstra (Structured Programming). It is a classic recursive backtracking approach. itQueenscBsSeZedZdZddZdZdZdZdZ dZ RS(cCs||_|jdS(N(tntreset(tselfR((s+/usr/lib64/python2.7/Demo/scripts/queens.pyt__init__s cCsf|j}dg||_dg||_dgd|d|_dgd|d|_d|_dS(Niii(RtNonetytrowtuptdowntnfound(RR((s+/usr/lib64/python2.7/Demo/scripts/queens.pyRs  icCsx}t|jD]l}|j||r|j|||d|jkrX|jn|j|d|j||qqWdS(Ni(trangeRtsafetplacetdisplaytsolvetremove(RtxR((s+/usr/lib64/python2.7/Demo/scripts/queens.pyRs cCs0|j| o/|j|| o/|j|| S(N(RRR (RRR((s+/usr/lib64/python2.7/Demo/scripts/queens.pyR &scCs@||j| s 8