[UVA] Non-boring sequences

题目:https://vjudge.net/problem/UVA-1608

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#pragma warning(disable:4996)
using namespace std;

const int maxn = 200000 + 5;
map cur;
int pre[maxn], nextt[maxn],a[maxn],n;
bool dfs(int L, int R)
{
	if (L >= R) return true;
	int mid;
	int s = L, e = R;
	while (s <= e)
	{
		if (pre[s] < L && nextt[s] > R)
		{
			mid = s;
			break;
		}

		if (pre[e] < L && nextt[e] > R)
		{
			mid = e;
			break;
		}
		s++; e--;
	}

	if (s > e) return false;
	return dfs(L, mid - 1) && dfs(mid + 1, R);
}


int main() {
	int kcase = 0;
	cin >> kcase;
	while (kcase--)
	{
		scanf("%d", &n);
		cur.clear();
		for (int i = 0; i < n; i++)
		{
			scanf("%d", &a[i]);
			if (!cur.count(a[i]))
			{
				pre[i] = -1;
			}
			else
			{
				pre[i] = cur[a[i]];
			}
			cur[a[i]] = i;
		}
		
		cur.clear();
		for (int i = n - 1; i >= 0; i--)
		{
			if (!cur.count(a[i]))
			{
				nextt[i] = n;
			}
			else
			{
				nextt[i] = cur[a[i]];
			}
			cur[a[i]] = i;
		}


		
		if (dfs(0, n - 1)) 
			cout << "non-boring\n";
		else
			cout << "boring\n";
	}
	
	return 0;
}

 

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