Submission #1136621

#	Time	Username	Problem	Language	Result	Execution time	Memory
1136621		steveonalex	Linear Garden (IOI08_linear_garden)	C++20	100 / 100	87 ms	62980 KiB

linear_garden

#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef unsigned long long ull;
 
#define MASK(i) (1ULL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
 
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(a, b);}
ll lcm(ll a, ll b){return a / gcd(a, b) * b;}
 
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ull mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
 
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
double rngesus_d(double l, double r){
    double cur = rngesus(0, MASK(60) - 1);
    cur /= MASK(60) - 1;
    return l + cur * (r - l);
}
 
template <class T1, class T2>
    bool maximize(T1 &a, T2 b){
        if (a < b) {a = b; return true;}
        return false;
    }
 
template <class T1, class T2>
    bool minimize(T1 &a, T2 b){
        if (a > b) {a = b; return true;}
        return false;
    }
 
template <class T>
    void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
        for(auto item: container) out << item << separator;
        out << finish;
    }
 
template <class T>
    void remove_dup(vector<T> &a){
        sort(ALL(a));
        a.resize(unique(ALL(a)) - a.begin());
    }

const int N = 1e6 + 69;
int n, MOD;
int dp[N][3];
string s;

int go_false(int digit, int cur){
    if (cur < 0 || cur > 2) return 0;
    if (n == digit) return 1;
    if (dp[digit][cur] != -1) return dp[digit][cur];
    int ans = 0;
    for(int i = -1; i <= 1; i += 2){
        ans += go_false(digit + 1, cur + i);
    }
    if (ans >= MOD) ans -= MOD;
    return dp[digit][cur] = ans;
}

int go_true(int digit, int cur){
    if (cur > 2 || cur < 0) return 0;
    if (digit == n) return 1;
    int r = -1;
    if (s[digit] == 'P') r = 1;
    int ans = go_true(digit + 1, cur + r);
    if (r > -1){
        ans += go_false(digit + 1, cur - 1);
        if (ans >= MOD) ans -= MOD;
    }
    return ans;
}

void sub(int &a, int b){
    a -= b;
    if (a < 0) a += MOD;
}

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

void solve(){
    memset(dp, -1, sizeof dp);
    cin >> n >> MOD;
    cin >> s;

    int nigga[3][3]; memset(nigga, 0, sizeof nigga);
    for(int i = 0; i < 3; ++i) for(int j = max(1, 2 - i); j <= 2; ++j) {
        if (j == 1){
            string tmp;
            if (i == 1) {
                for(int t = 0; t < n; ++t) {
                    if (t % 2) tmp.push_back('P');
                    else tmp.push_back('L');
                }
            }
            else{
                for(int t = 0; t < n; ++t) {
                    if (t % 2) tmp.push_back('L');
                    else tmp.push_back('P');
                }
            }
            if (tmp <= s) nigga[i][j]++;
        }
        else if (j == 2){
            memset(dp, -1, sizeof dp);
            nigga[i][j] = go_true(0, 2-i);
        }
    }

    int ans = 0;
    for(int i = 0; i < 3; ++i) {
        for(int j = 2 - i; j <= 2; ++j) if (j != 1) {
            add(ans, nigga[i][j]);
        }
    }
    sub(ans, nigga[1][1]); sub(ans, nigga[2][1]);
    cout << ans << "\n";
}

int main(void){
    ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);

    clock_t start = clock();

    solve();

    cerr << "Time elapsed: " << clock() - start << " ms\n";
    return 0;
}

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