2011年11月6日
#91 E
摘要： problem linkhttp://codeforces.com/contest/122/problem/ELucky number contains only 4s and/or 7s, find the amount of lucky number whose postion also a lucky number of the Kth permutation of a 10^9 long seqence sort lexicographically.What a dam thing? Calm down to analyse, no big deal.First thing to do 阅读全文
posted @ 2011-11-06 20:00 DOF_KL 阅读(1138) 评论(0) 推荐(0) 编辑
#90 C
摘要： problem linkhttp://codeforces.com/contest/119/problem/CA classic dp problem, even though I knew this I still spent much time on figuring out the solution.As solving most dp problem, the difficult point is to find out the state transition equation.Before working on the state transition equation, I ne 阅读全文
posted @ 2011-11-06 19:09 DOF_KL 阅读(163) 评论(0) 推荐(0) 编辑