poj 3320 Jessica's Reading Problem 【尺取法+STLmap set】



Jessica's Reading Problem

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 7893		Accepted: 2529

Description

Jessica's a very lovely girl wooed by lots of boys. Recently she has a problem. The final exam is coming, yet she has spent little time on it. If she wants to pass it, she has to master all ideas included in a very thick text book. The author of that text book, like other authors, is extremely fussy about the ideas, thus some ideas are covered more than once. Jessica think if she managed to read each idea at least once, she can pass the exam. She decides to read only one contiguous part of the book which contains all ideas covered by the entire book. And of course, the sub-book should be as thin as possible.

A very hard-working boy had manually indexed for her each page of Jessica's text-book with what idea each page is about and thus made a big progress for his courtship. Here you come in to save your skin: given the index, help Jessica decide which contiguous part she should read. For convenience, each idea has been coded with an ID, which is a non-negative integer.

Input

The first line of input is an integer P (1 ≤ P ≤ 1000000), which is the number of pages of Jessica's text-book. The second line containsP non-negative integers describing what idea each page is about. The first integer is what the first page is about, the second integer is what the second page is about, and so on. You may assume all integers that appear can fit well in the signed 32-bit integer type.

Output

Output one line: the number of pages of the shortest contiguous part of the book which contains all ideals covered in the book.

Sample Input

5
1 8 8 8 1

Sample Output

2

题意：要复习P页的书籍，每页都有一个知识点，同一个知识的可能出现在不同页。问最少需要看的连续的页数才能看完所有的知识点。

尺取法：从区间的起始和结尾进行修改和更新。

思路：首先找到最初能够覆盖所有知识点的连续的页（用一个变量num来记录已出现的不同的知识点，用s表示区间头部，t表示区间尾部），若不能找到，说明从当前区间头部到最后一页的整个区间都不能覆盖所有知识点，那么不用往后找了，跳出；若能找到就更新区间长度，然后修改区间头部，（这里要注意：若区间头部对应的知识点在当前区间只出现一次就把知识点总数num减一）。下面操作一样的，不断更新与修改，直到当前区间头部->最后一页不能覆盖所有知识为止。

提醒：我们用知识点和出现在当前区间的次数建立映射map，用set来记录不同的知识的个数。

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