Submission #782518

#	Time	Username	Problem	Language	Result	Execution time	Memory
782518		phoebe	Linear Garden (IOI08_linear_garden)	C++17	85 / 100	59 ms	65536 KiB

linear_garden

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

// #define int long long
#define ll long long
#define pii pair<int, int>
#define F first
#define S second
#define PB push_back
#define ALL(x) x.begin(), x.end()
#define FOR(i, n) for (int i = 0; i < n; i++)
#define NYOOM ios::sync_with_stdio(0); cin.tie(0);
#define endl '\n'
const int INF = 1e9 + 7;
const ll LLINF = 1ll<<60;

const int maxn = 1e6 + 10;
int n, m, dp[3][3][maxn];
string s; 

int cnt(int mn, int mx, int rem){ // mn = min(l - p), mx = max(l - p)
    if (mn <= -3 || mx >= 3) return 0;
    if (rem <= 0) return 1;
    if (dp[-mn][mx][rem] != -1) return dp[-mn][mx][rem];
    int go_l = cnt(min(mn + 1, 0), mx + 1, rem - 1);
    int go_p = cnt(mn - 1, max(0, mx - 1), rem - 1);
    dp[-mn][mx][rem] = (go_l + go_p) % m;
    return dp[-mn][mx][rem];
}

signed main(){
    NYOOM;
    fill(&dp[0][0][0], &dp[0][0][0] + 3 * 3 * maxn, -1);
    cin >> n >> m;
    cin >> s;
    int re = 1, mn = 0, mx = 0;
    FOR(i, n){
        if (s[i] == 'L'){
            mn = min(0, mn + 1), mx = mx + 1;
            continue;
        }
        // cur is p
        int rem = n - i - 1;
        int go_l = cnt(min(mn + 1, 0), mx + 1, rem);
        mn = mn - 1, mx = max(0, mx - 1);
        re = (re + go_l) % m;
    }
    cout << re;
}

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