Submission #970376

#	Time	Username	Problem	Language	Result	Execution time	Memory
970376		starchan	Linear Garden (IOI08_linear_garden)	C++17	65 / 100	15 ms	65536 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][MX];

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

	return dp[m][M][cur][K] = (opt1+opt2)%mod;
}

int whatifL(int m, int M, int cur, int K)
{
	if((M > 2) || (cur > M) || (cur < 0) || (m < 0))
		return 0;
	if(K == 0)
		return 0;
	int m1 = m+min(0, cur-1); int opt1 = solve(m1, M+m-m1, cur+m-m1-1, K-1);
	return opt1;
}

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++)
			{
				for(int ell = 0; ell < n; ell++)
					dp[i][j][k][ell] = -1;
			}
		}
	}
	vector<int> a(n+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')
			ans+=whatifL(m, M-m, cur-m, K);
		K--; cur = a[i];
		m = min(m, a[i]); M = max(M, a[i]);
		ans%=mod;
	}
	ans++; ans%=mod;
	cout << ans << "\n";
	return 0;
}	

Compilation message (stderr)

linear_garden.cpp: In function 'int main()':
linear_garden.cpp:64:32: warning: the omitted middle operand in '?:' will always be 'true', suggest explicit middle operand [-Wparentheses]
   64 |   a[i] = a[i-1] + ((c == 'P') ?: -1);
      |                                ^

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