永夜莫明的博客

http://icpc.upc.edu.cn/problem.php?cid=1822&pid=8题目描述Tom has a string containing only lowercase letters. He wants to choose a subsequence of the string whose length is k and lexicographical or...

https://nanti.jisuanke.com/t/41389The value of a string s is equal to the number of different letters which appear in this string.Your task is to calculate the total value of all the palindrome su...