这是一段简要说明，摘自Tom Verhoeff关于IOI'94的报告
Given a state of the dials, find a shortest sequence of moves to make all dials
 point up. This is not such a difficult problem. A first important observation 
is that reordering the moves in a sequence does not affect the result 
(superposition principle). A second observation transforms it into a linear 
algebra problem, involving nine linear equations in nine unknowns ($x_i$ 
indicates how often move $i$ occurs). The inversion of the resulting 
9x9-matrix can in fact be done off-line, since it is fixed. This yields an 
extremely fast and short program.

• Re:不明白，老师没说过，能解释一下吗？或者哪里可以查的到？ (51) baicaited 2009-04-10 19:46:26