记录编号	601941	评测结果	AAAAAATTTTTTTTTTTTTT
题目名称	3947.[国家集训队 2011]等差子序列	最终得分	30
用户昵称	OTTF	是否通过	未通过
代码语言	C++	运行时间	3.231 s
提交时间	2025-06-29 17:54:18	内存使用	3.84 MiB

#include <cstring>
#include <cstdio>
#include <iostream>

using namespace std;

constexpr int N = 21145;

int t;
int n;
bool flag[N];

int main () {
	
	freopen ("sequence.in", "r", stdin);
	freopen ("sequence.out", "w", stdout);

	scanf ("%d", &t);

	for (int index = 1; index <= t; index++) {
		scanf ("%d", &n);
		memset (flag, 0, sizeof (flag));
		int num;
		char ch = 'N';
		for (int i = 1; i <= n; i++) {
			scanf ("%d", &num);
			if (ch == 'Y') {
				continue;
			}
			for (int j = 1; j < num; j++) {
				if (num + (num - j) <= n && (flag[j] ^ flag[num + (num - j)])) {
					ch = 'Y';
				}
			}
			flag[num] = true;
		}
		printf ("%c\n", ch);
	}
	
	return 0;
}