Submission #1232908

#	Time	Username	Problem	Language	Result	Execution time	Memory
1232908		lanaskarica	Linear Garden (IOI08_linear_garden)	C++20	95 / 100	53 ms	71908 KiB

linear_garden

#include <bits/stdc++.h>
using namespace std;

#define ll long long 
#define pii pair <int, int>
#define fi first
#define se second

const int MAXN = 1e6 + 1;

int MOD, dp[MAXN][3][3][2];

int add(int a, int b) {
	a += b;
	if (a >= MOD) a -= MOD;
	return a;
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	
	string s;
	int n;
	cin >> n >> MOD >> s;
	
	dp[1][1][0][0] = 1;
	dp[1][0][1][1] = 1;
	
	for (int i = 2; i <= n; i++) {
		for (int j = 1; j <= 2; j++) {
			dp[i][j][0][0] = dp[i - 1][j - 1][0][0];
			dp[i][0][j][1] = dp[i - 1][0][j - 1][1];
			for (int z = 0; z <= 1; z++) {
				dp[i][j][z][0] = add(dp[i][j][z][0], dp[i - 1][j - 1][z + 1][0]);	
				dp[i][j][z][0] = add(dp[i][j][z][0], dp[i - 1][j - 1][z + 1][1]);
				
				dp[i][z][j][1] = add(dp[i][z][j][1], dp[i - 1][z + 1][j - 1][0]);	
				dp[i][z][j][1] = add(dp[i][z][j][1], dp[i - 1][z + 1][j - 1][1]);
			}
		}
	}
	
	int rj = 0, x = 0, y = 0;
	for (int i = 0; i < n; i++) {
		if (s[i] == 'L') {
			x++; y = max(0, y - 1);
			continue;
		}
		for (int j = 0; j <= (2 - x); j++) {
			for (int z = 0; z <= (2 - y); z++) {
				rj = add(rj, dp[n - i][j][z][0]);
			}
		}
		x = max(0, x - 1); y++;
	}
	cout << add(rj, 1) << "\n";
	
	return 0;
}

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