回复：Hint

Let's start with smallest number of coins 50+20+20+2

There are only two possibilities for a 5: one 5 or five 1s.

There are four possibilities for a 10: one 10, two 5s, one 5 and five 1s, or ten 1s

There are two ways for a 20: one 20 or two 10s.

There are three ways for a 50: one 50, five 10s or 20,20 and 10.

所有跟帖： 

• 回复：correction -NaCl- ♂ (87 bytes) () 12/18/2007 postreply 20:42:47

• thank you -janewwwu- ♀ (2 bytes) () 12/18/2007 postreply 22:38:32