Codeforce - 352B - Jeff and Periods

最新推荐文章于 2022-02-18 14:33:15 发布

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最新推荐文章于 2022-02-18 14:33:15 发布 · 408 阅读

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该博客讨论了如何解决一个编程问题，即给定一个整数序列，找出所有满足条件的元素x：x在序列中出现且所有x的位置形成一个等差数列。通过输入示例和题目说明解释了问题，提出了解决方案，并提供了通过测试的代码实现。

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B. Jeff and Periods
time limit per test1 second
memory limit per test256 megabytes
inputstandard input
outputstandard output
One day Jeff got hold of an integer sequence a1, a2, …, an of length n. The boy immediately decided to analyze the sequence. For that, he needs to find all values of x, for which these conditions hold:

x occurs in sequence a.
Consider all positions of numbers x in the sequence a (such i, that ai = x). These numbers, sorted in the increasing order, must form an arithmetic progression.
Help Jeff, find all x that meet the problem conditions.

Input
The first line contains integer n (1 ≤ n ≤ 105). The next line contains integers a1, a2, …, an (1 ≤ ai ≤ 105). The numbers are separated by spaces.

Output
In the first line print integer t — the number of valid x. On each of the next t lines print two integers x and px, where x is current suitable valu