摘要：The only difference between the easy and the hard versions is constraints. A subsequence is a string that can be derived from another string by deleti 阅读全文

摘要：1095 解码PAT准考证/1153 Decode Registration Card of PAT（25 分） PAT 准考证号由 4 部分组成： 第 1 位是级别，即 T 代表顶级；A 代表甲级；B 代表乙级； 第 2~4 位是考场编号，范围从 101 到 999； 第 5~10 位是考试日期， 阅读全文

摘要：String Given a string S and two integers L and M, we consider a substring of S as “recoverable” if and only if (i) It is of length M*L; (ii) It can be 阅读全文

摘要：The kth great number Xiao Ming and Xiao Bao are playing a simple Numbers game. In a round Xiao Ming can choose to write down a number, or ask Xiao Bao 阅读全文