∑m=1min(L,R)CL−1m−1CLm\sum_{m=1}^{\min(L,R)} \frac{C_{L-1}^{m-1}}{C_{L}^m}∑m=1min(L,R)CLmCL−1m−1
∑m=1min(L,R)CR−1m−1CRm\sum_{m=1}^{\min(L,R)} \frac{C_{R-1}^{m-1}}{C_{R}^m}∑m=1min(L,R)CRmCR−1m−1
这两个式子可以化简成 O(1)O(1)O(1) 求吗
