一只大象带着一只小象,一只老虎带着一只小老虎,一只狮子带着一只小狮子它们来到河边,都要过河,

A大象B老虎C狮子a小象b小老虎c小狮子
1 ab到对岸 `````````` ab
2 a 回来 ```````````` a
3 ac到对岸``````````` ab
4 a回来 ``````````` bc
5 BC到对岸 `````````` BCbc
6 Bb回来 ``````````` Cc
7 Aa到对岸```````````ACac
8 Cc回来 ``````````` Aa
9 BC到对岸 ``````````ABCa
10 a回来 ``````````` ABC
11 ac到对岸 `````````` ABCac
12 B回来 ```````````` ACac
13 Bb到对岸`````````` ABCabc