Submission #429816

#	Time	Username	Problem	Language	Result	Execution time	Memory
429816		arayi	Linear Garden (IOI08_linear_garden)	C++17	85 / 100	72 ms	65540 KiB

linear_garden

//Arayi
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <string>
#include <queue>
#include <stack>
#include <algorithm>
#include <math.h>   
#include <vector>
#include <cstring>
#include <ctime>
#include <set>
#include <bitset>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <ctime>
#include <climits>
#include <cassert>
#include <chrono>
#include <random>
#include <complex>

#define fr first
#define sc second
#define MP make_pair
#define ad push_back
#define PB push_back
#define fastio ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define lli long long int
#define y1 arayikhalatyan
#define j1 jigglypuff
#define ld long double
#define itn int
#define pir pair<int, int>
#define all(x) (x).begin(), (x).end()
#define str string
#define enl endl
#define en endl
#define cd complex<long double>
#define vcd vector<cd>
#define vii vector<int>
#define vlli vector<lli>
using namespace std;


const int N = 1e6 + 30;
lli mod = 1e9 + 7;


int n;
str s;
lli ans = 1, dp1[2][N][3], dp[N][4][3];
int main()
{
    fastio;
    //freopen("input.in", "r", stdin);
    cin >> n >> mod >> s;
    dp1[0][0][1] = 1;
    dp1[1][0][2] = 1;
    for (int i = 1; i <= n; i++)
    {
        for(auto i1 : {0, 1})
        {
            for(auto i2 : {1, 2}) dp1[i1][i][i2] = dp1[i1][i-1][i2-1];
            for(auto i2 : {0, 1}) dp1[i1][i][i2] += dp1[i1][i-1][i2+1], dp1[i1][i][i2] %= mod;
        }
    }
    dp[0][2][0] = 1;
    for (int i = 1; i <= n; i++)
    {
        for(auto i1 : {1, 2}) dp[i][i1 + 1][1] += dp[i-1][i1][1];
        for(auto i1 : {2, 3}) dp[i][i1 - 1][1] += dp[i-1][i1][1], dp[i][i1-1][1]%=mod;
        for(auto i1 : {0, 1}) dp[i][i1 + 1][2] += dp[i-1][i1][2];
        for(auto i1 : {1, 2}) dp[i][i1 - 1][2] += dp[i-1][i1][2], dp[i][i1-1][2]%=mod;
        dp[i][2][0] += dp[i-1][1][0], dp[i][1][0] += dp[i-1][2][0];
        dp[i][3][1] += dp[i-1][2][0]; dp[i][3][1] %= mod;
        dp[i][0][2] += dp[i-1][1][0]; dp[i][0][2] %= mod;
    }
    int mn = 0, mx = 0;
    for (int i = 0; i < n; i++)
    {
        if(s[i] == 'L')
        {
            mn = min(0, mn + 1);
            mx++;
        }
        else
        {
            int mn1 = min(0, mn + 1);
            int mx1 = mx + 1;
            if(mx1 - mn1 <= 2)
            {
                if(mx1 == 2) for(auto i1 : {0,1,2}) ans += dp1[1][n-i-1][i1];
                else if(mx1 - mn1 == 2) for(auto i1 : {0,1,2}) ans += dp1[0][n-i-1][i1];
                else for(auto i1 : {0,1,2,3}) {for(auto i2 : {0,1,2}) ans += dp[n-i-1][i1][i2];}
                ans %= mod;
            }
            mn--;
            mx=max(0, mx-1);
        }
        //cout << ans << " ";
    }
    cout<<ans<<endl;
    return 0;
}

/*
    __
  *(><)*
    \/ /
    ||/
  --||
    ||
    /\
   /  \
  /    \

*/

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