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The Little Elephant loves strings very much. He has an array a from n strings, consisting of lowercase English letters. Let's number the elements of t 阅读全文
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题目:CodeForces196-D:The Next Good String 题意:给定仅由小写字母组成的字符串S和一个正整数m。求一个长度与S相同的仅由小写字母组成的字符串S1,满足: S1的字典序>S的字典序 S1中不含长度大于等于d的回文串。 思路:许昊然的文章里叫“逐位确定法”,以为之前没 阅读全文
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Rubik is very keen on number permutations. A permutation a with length n is a sequence, consisting of n different numbers from 1 to n. Element number 阅读全文