答案:选一个囚犯出来负责关灯,其余的负责开灯,而且每人只能开一次,当这个囚犯关够99次的时候,就知道所有的囚犯都来过院子了。 5 t6 B8 b' C) e1 C; u, W8 Z5.39.217.76 $ j) b! t3 I8 a' |" p( f' Ti don't get it.. how to pick someone to record it.. when there is only 1 person allow to go out each day..and he/she will lock up later