Submission #121953

#	Time	Username	Problem	Language	Result	Execution time	Memory
121953		nvmdava	Linear Garden (IOI08_linear_garden)	C++17	100 / 100	35 ms	22036 KiB

linear_garden

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

string s;
int dp3[1000005][3];
int dp2[1000005][2];
int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int n, m;
	cin>>n>>m;
	cin>>s;
	dp3[1][0] = 1;
	dp3[1][1] = 1;
	dp3[1][2] = 1;
	dp2[1][0] = 1;
	dp2[1][1] = 1;
	for(int i = 2; i <= n; i++){
		dp3[i][0] = dp3[i - 1][1];
		dp3[i][2] = dp3[i - 1][1];
		dp3[i][1] = dp3[i - 1][0] + dp3[i - 1][2];
		dp3[i][1] %= m;
		dp2[i][0] = dp2[i - 1][1] + dp3[i - 1][0];
		dp2[i][1] = dp2[i - 1][0] + dp3[i - 1][2];
		dp2[i][1] %= m;
		dp2[i][0] %= m;
	}
	int mx = 0, mn = 0, now = 0, ans = 0;
	for(int i = 0; i < n; i++){
		if(s[i] == 'P' && mx < now + 2){
			int dec = (mx - min(now - 1, mn)) * 3 + ((now - 1) - min(now - 1, mn)) - 3;
			if(dec == 0) ans += dp2[n - i][0];
			else if(dec == 1) ans += dp2[n - i][1];
			else if(dec == 3) ans += dp3[n - i][0];
			else if(dec == 4) ans += dp3[n - i][1];
			else if(dec == 5) ans += dp3[n - i][2];
			
			ans %= m;
		}
		if(s[i] == 'P') now++;
		if(s[i] == 'L') now--;
		mx = max(mx, now);
		mn = min(mn, now);
	}
	cout<<(ans + 1) % m;
}

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