因为6 == 3+3 == 1+2+3 == 2+2+2,
选法总数为:
6*5/(2*1) + 6*5*4 + 6*5*4/(3*2*1)
==15 + 120 + 20
==155,
问者应该有答案,看看对不,不对再另想办法!