can be done in linear time...

find i such that a[i] != i

Let us assume i = 1

a[1], a[a[1]], ..., a^{n}[1] can be viewed as a single linked list...

2x chase...

所有跟帖： 

• it takes a bit more than that -dynamic- ♂ (438 bytes) () 05/18/2009 postreply 19:55:29

• hmm，這個有意思：） -戲雨飛鷹- ♀ (0 bytes) () 05/18/2009 postreply 21:12:19

• 回複：it takes a bit more than that -utopian- ♂ (51 bytes) () 05/20/2009 postreply 17:23:11

• hashing needs linear memory as well. we want constant memory her -dynamic- ♂ (0 bytes) () 05/20/2009 postreply 17:28:12

• Pay attention to some key numbers. -亂彈- ♂ (0 bytes) () 05/20/2009 postreply 19:24:24

• 覺得在哪裏見過這個題目 -haha2000- ♂ (19 bytes) () 05/21/2009 postreply 07:24:10

• I don't think so. -亂彈- ♂ (0 bytes) () 05/21/2009 postreply 09:52:29

• 這題目是IMB ２００４ 一月的一個puzzle：） -戲雨飛鷹- ♀ (79 bytes) () 05/21/2009 postreply 12:22:12

• Yes, right! thanks! -haha2000- ♂ (0 bytes) () 05/22/2009 postreply 11:05:23