9A = 9 * 16 + 10 = 154
232 = 2 * 64 + 26 = 128 + 26 = 154
左根右
4 + 3 + 2 + 1
C
B
A
AAABBBCCC
长度为1：A B C 3
2：AA AB BB BC CC 5
3：AAA AAB ABB BBB BBC BCC CCC 7
4：AAAB AABB ABBB BBBC BBCC BCCC 6
5：AAABB AABBB ABBBC BBBCC BBCCC 5
6：AAABBB AABBBC ABBBCC BBBCCC 4
7：AAABBBC AABBBCC ABBBCCC 3
8：AAABBBCC AABBBCCC 2
9: AAABBBCCC 1
5!*5!/5=14400/5=2880种
两个5!分别是大陆选手和港澳选手的就坐方案,相乘后,再除以5中重复的方案.
5！*5！*2/10=28800/10=2880