10513 - 乐曲主题

我们用N(1 <= N <=5000)个音符的序列来表示一首乐曲，每个音符都是1..88范围内的整数，每个数表示钢琴上的一个键。很不幸这种表示旋律的方法忽略了音符的时值，但这项编程任务是关于音高的，与时值无关。

许多作曲家围绕一个重复出现的“主题”来构建乐曲。在我们的乐曲表示法中，“主题”是整个音符序列的一个子序列，它需要满足如下条件：

长度至少为5个音符 在乐曲中重复出现(可能经过转调，见下) 重复出现的同一主题不能重叠 “转调”的意思是主题序列中每个音符都被加上或减去了同一个整数值。 给定一段乐曲，计算其中最长主题的长度(即音符数)。

本题时限为1秒钟!

输出文件的第一行包含整数N。下面的每一行(最后一行可能除外)包含20个整数，表示音符序列。最后一行可能少于20个音符。

输出文件应只含一个整数，即最长主题的长度。如果乐曲中没有主题，那么输出0。

Musical Themes Brian Dean A musical melody is represented as a sequence of N (1 <= N <= 5000) notes that are integers in the range 1..88, each representing a key on the piano. It is unfortunate but true that this representation of melodies ignores the notion of musical timing; but, this programming task is about notes and not timings.

Many composers structure their music around a repeating "theme", which, being a subsequence of an entire melody, is a sequence of integers in our representation. A subsequence of a melody is a theme if it:

is at least five notes long appears (potentially transposed -- see below) again somewhere else in the piece of music is disjoint from (i.e., non-overlapping with) at least one of its other appearance(s) Transposed means that a constant positive or negative value is added to every note value in the theme subsequence. Given a melody, compute the length (number of notes) of the longest theme.

One second time limit for this problem's solutions!

PROGRAM NAME: theme INPUT FORMAT The first line of the input file contains the integer N. Each subsequent line (except potentially the last) contains 20 integers representing the sequence of notes. The last line contains the remainder of the notes, potentially fewer than 20.

SAMPLE INPUT (file theme.in) 30 25 27 30 34 39 45 52 60 69 79 69 60 52 45 39 34 30 26 22 18 82 78 74 70 66 67 64 60 65 80

OUTPUT FORMAT The output file should contain a single line with a single integer that represents the length of the longest theme. If there are no themes, output 0.

SAMPLE OUTPUT (file theme.out) 5

[The five-long theme is the last five notes of the first line and the first five notes of the second]