BZOJ 2729 HNOI2012 排队 组合数学

题目大意：给定n个男生m个女生两个老师，求有多少种排列满足任意两个女生不相邻，任意两个老师也不相邻

def A(n):
	re=1
	for i in range(1,n+1):
		re*=i
	return re
def C(n,m):
	if n<m:
		return 0
	return A(n)//A(m)//A(n-m)
n,m=[int(i) for i in raw_input().split()]
print m*A(n+1)*2*A(m-1)*C(n+2,m-1)+(A(n+2)-A(n+1)*2)*A(m)*C(n+3,m)