NephrenRuqInsania

题目描述 Farmer John has recently purchased a new barn containing N milking machines (1 <= N <= 40,000), conveniently numbered 1…N and arranged in a row. Milking machine i is capable of extracting M...

这题真的是“写题五分钟，想题两小时”啊 我们考虑一个dpdpdp，我们用dpi,jdp_{i,j}dpi,j​表示第一排匹配到iii，第二排匹配到jjj,并且i,ji,ji,j相匹配 那么转移方程就是 dpi,j=max⁡{dpk,j}+1,k<i,bj∈[max⁡(1,ai−4),max⁡(n,ai+4)]dp_{i,j}=\max\{dp_{k,j}\}+1,k< i,b_j\in...