Submission #970401

#	Time	Username	Problem	Language	Result	Execution time	Memory
970401		starchan	Linear Garden (IOI08_linear_garden)	C++17	100 / 100	143 ms	17084 KiB

linear_garden

#include<bits/stdc++.h>
using namespace std;
#define in array<int, 2>
#define pb push_back
#define pob pop_back
#define INF (int)1e17
#define fast() ios_base::sync_with_stdio(false); cin.tie(NULL)

const int MX = 1e6+3;

int mod;

int dp[3][3][3];
int tmp[3][3][3];

int dd(int m, int M, int cur)
{
	if((M > 2) || (cur > M) || (cur < 0) || (m < 0))
		return 0;
	else
		return dp[m][M][cur];
}

int solve(int m, int M, int cur)
{
	if((M > 2) || (cur > M) || (cur < 0) || (m < 0))
		return 0;
	
	int m1 = m+min(0, cur-1); int opt1 = dd(m1, M+m-m1, cur+m-m1-1);
	int M2 = max(M, cur+1); int opt2 = dd(m, M2, cur+1);

	return (opt1+opt2)%mod;
}

array<int, 3> whatifL(int m, int M, int cur, int K)
{
	if((M > 2) || (cur > M) || (cur < 0) || (m < 0))
		return {-1, -1, -1};
	int m1 = m+min(0, cur-1); 
	return {m1, M+m-m1, cur+m-m1-1};
}

signed main()
{
	fast();
	int n;
	cin >> n >> mod;
	for(int i = 0; i < 3; i++)
	{
		for(int j = 0; j < 3; j++)
		{
			for(int k = 0; k < 3; k++)
				dp[i][j][k] = 1;
		}
	}

	vector<int> a(n+1);
	vector<array<int, 3>> Q(n+1, {-1});
	a[0] = 2;
	int m, M, cur, K;
	int ans = 0;
	m = M = cur = 2; K = n;
	for(int i = 1; i <= n; i++)
	{
		char c; cin >> c;
		a[i] = a[i-1] + ((c == 'P') ?: -1);
		if(c == 'P')
			Q[K] = whatifL(m, M-m, cur-m, K);
		K--; cur = a[i];
		m = min(m, a[i]); M = max(M, a[i]);
	}
	for(int i = 1; i <= n; i++)
	{
		auto [mv, Mv, curv] = Q[i];
		if(m == -1)
			continue;
		if((Mv <= 2) && (curv <= Mv) && (curv >= 0) && (mv >= 0))
			ans+=dp[mv][Mv][curv];
		for(int m = 0; m < 3; m++)
		{
			for(int M = 0; M < 3; M++)
			{
				for(int cur = 0; cur <= M; cur++)
					tmp[m][M][cur] = solve(m, M, cur);
			}
		}
		ans%=mod;
		swap(dp, tmp);
	}
	ans++; ans%=mod;
	cout << ans << "\n";
	return 0;
}	

Compilation message (stderr)

linear_garden.cpp: In function 'int main()':
linear_garden.cpp:66:32: warning: the omitted middle operand in '?:' will always be 'true', suggest explicit middle operand [-Wparentheses]
   66 |   a[i] = a[i-1] + ((c == 'P') ?: -1);
      |                                ^

• Subtask 1: 2 / 2
• Subtask 2: 2 / 2
• Subtask 3: 4 / 4
• Subtask 4: 4 / 4
• Subtask 5: 4 / 4
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