|
|
original poster
hbghlyj
posted 2019-10-2 16:41
回复 1# hbghlyj
设有$\lambda_i$条直线共点(i=1,2...k)，$u_j$条直线平行(j=1,2...h)，问题等价于:
$f(n)=\sum_{i=1}^kC^2_{\lambda_i-1}+\sum_{j=1}^hC_{u_j}^2$当i=1,2...k，j=1,2...h，$\lambda_i\geq3,\Sigma\lambda_i\leq n,\Sigma u_i\leq n$时跑遍$\{n+1,n+2\cdots C_n^2+2,C_n^2+n,C_n^2+n-1\}$ |
|
