CF1203A.Circle of Students
入门
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时间限制:2.00s
内存限制:256MB
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题目描述
There are n students standing in a circle in some order. The index of the i-th student is pi. It is guaranteed that all indices of students are distinct integers from 1 to n (i. e. they form a permutation).
Students want to start a round dance. A clockwise round dance can be started if the student 2 comes right after the student 1 in clockwise order (there are no students between them), the student 3 comes right after the student 2 in clockwise order, and so on, and the student n comes right after the student n−1 in clockwise order. A counterclockwise round dance is almost the same thing — the only difference is that the student i should be right after the student i−1 in counterclockwise order (this condition should be met for every i from 2 to n).
For example, if the indices of students listed in clockwise order are [2,3,4,5,1], then they can start a clockwise round dance. If the students have indices [3,2,1,4] in clockwise order, then they can start a counterclockwise round dance.
Your task is to determine whether it is possible to start a round dance. Note that the students cannot change their positions before starting the dance; they cannot swap or leave the circle, and no other student can enter the circle.
You have to answer q independent queries.
有 n 名学生按某种顺序围成一个圆圈站立。第 i 个位置上的学生的编号为 pi。保证所有学生的编号均为 1 到 n 之间的互不相同的整数(即它们构成一个排列)。
学生们希望开始一场“环形舞”(round dance)。若在顺时针方向上,学生 2 紧跟在学生 1 之后(二者之间没有其他学生),学生 3 紧跟在学生 2 之后,……,学生 n 紧跟在学生 n−1 之后,则可以开始一场顺时针环形舞。而逆时针环形舞则几乎相同,唯一的区别是:对每个 i(从 2 到 n),学生 i 必须在逆时针方向上紧跟在学生 i−1 之后。
例如,若学生编号按顺时针顺序排列为 [2,3,4,5,1],则他们可以开始一场顺时针环形舞。若学生编号按顺时针顺序排列为 [3,2,1,4],则他们可以开始一场逆时针环形舞。
你的任务是判断是否可能开始一场环形舞。注意:在开始舞蹈前,学生不能改变自己的位置;他们既不能交换位置,也不能离开圆圈,也不允许其他学生加入圆圈。
你需要回答 q 个相互独立的查询。
输入格式
The first line of the input contains one integer q (1≤q≤200) — the number of queries. Then q queries follow.
The first line of the query contains one integer n (1≤n≤200) — the number of students.
The second line of the query contains a permutation of indices p1,p2,…,pn (1≤pi≤n), where pi is the index of the i-th student (in clockwise order). It is guaranteed that all pi are distinct integers from 1 to n (i. e. they form a permutation).
输入的第一行包含一个整数 q(1≤q≤200),表示查询次数。随后是 q 次查询。
每次查询的第一行包含一个整数 n(1≤n≤200),表示学生的数量。
每次查询的第二行包含一个索引的排列 p1,p2,…,pn(1≤pi≤n),其中 pi 表示顺时针方向上第 i 个学生的编号。保证所有 pi 均为 1 到 n 之间互不相同的整数(即构成一个排列)。
输出格式
For each query, print the answer on it. If a round dance can be started with the given order of students, print "YES". Otherwise print "NO".
对于每个查询,请输出其答案。如果能以给定的学生顺序开始圆圈舞,则输出 “YES”;否则输出 “NO”。
输入输出样例
输入#1
5 4 1 2 3 4 3 1 3 2 5 1 2 3 5 4 1 1 5 3 2 1 5 4
输出#1
YES YES NO YES YES
输入解题思路,AI测评打分。不知道怎么写?