A10015 | LCS Again
时间限制1s
内存限制256MB
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题目描述
You are given a string $S$ of length $n$ with each character being one of the first $m$ lowercase English letters.
Calculate how many different strings $T$ of length $n$ composed from the first $m$ lowercase English letters exist such that the length of LCS (longest common subsequence) between $S$ and $T$ is $n-1$ .
Recall that LCS of two strings $S$ and $T$ is the longest string $C$ such that $C$ both in $S$ and $T$ as a subsequence.
Calculate how many different strings $T$ of length $n$ composed from the first $m$ lowercase English letters exist such that the length of LCS (longest common subsequence) between $S$ and $T$ is $n-1$ .
Recall that LCS of two strings $S$ and $T$ is the longest string $C$ such that $C$ both in $S$ and $T$ as a subsequence.
输入格式
The first line contains two numbers $n$ and $m$ denoting the length of string $S$ and number of first English lowercase characters forming the character set for strings ( $1<=n<=100000$ , $2<=m<=26$ ).
The second line contains string $S$ .
The second line contains string $S$ .
输出格式
Print the only line containing the answer.
输入输出样例
输入 #1
3 3 aaa
输出 #1
6
输入 #2
3 3 aab
输出 #2
11
输入 #3
1 2 a
输出 #3
1
输入 #4
10 9 abacadefgh
输出 #4
789
For the first sample, the $6$ possible strings $T$ are: aab, aac, aba, aca, baa, caa.
For the second sample, the $11$ possible strings $T$ are: aaa, aac, aba, abb, abc, aca, acb, baa, bab, caa, cab.
For the third sample, the only possible string $T$ is b.
For the second sample, the $11$ possible strings $T$ are: aaa, aac, aba, abb, abc, aca, acb, baa, bab, caa, cab.
For the third sample, the only possible string $T$ is b.
C++ 编辑器
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评测结果：Accepted