Submission #1092622

#	Time	Username	Problem	Language	Result	Execution time	Memory
1092622		Whisper	NoM (RMI21_nom)	C++17	100 / 100	90 ms	612 KiB

Main

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

#define int long long
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define FORD(i, a, b) for (int i = (b); i >= (a); i --)
#define REP(i, a) for (int i = 0; i < (a); ++i)
#define REPD(i, a) for (int i = (a) - 1; i >= 0; --i)

#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)


constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

/*
    Phu Trong from Nguyen Tat Thanh High School for gifted student
*/

template <class X, class Y>
    bool minimize(X &x, const Y &y){
        X eps = 1e-9;
        if (x > y + eps) {x = y; return 1;}
        return 0;
    }

template <class X, class Y>
    bool maximize(X &x, const Y &y){
        X eps = 1e-9;
        if (x + eps < y) {x = y; return 1;}
        return 0;
    }
#define MAX                 4004
int N, M;
int dp[2][MAX];

int cnt[MAX];
int inv[MAX], fac[MAX];
int power(int a, int exp){
    int res = 1;
    for (; exp > 0; exp >>= 1, a = (1LL * a * a) % Mod) if(exp & 1){
        res = (1LL * res * a) % Mod;
    }
    return res;
}

void genFac(int n){
    fac[0] = 1;
    for (int i = 1; i <= n; ++i) fac[i] = fac[i - 1] * i % Mod;
    inv[n] = power(fac[n], Mod - 2);
    for (int i = n - 1; i >= 0; --i) inv[i] = inv[i + 1] * (i + 1) % Mod;
}

int C(int n, int k){
    if (n < k) return 0;
    return fac[n] * inv[k] % Mod * inv[n - k] % Mod;
}
int A(int n, int k){
    if (n < k) return 0;
    return fac[n] * inv[n - k] % Mod;
}
void add(int &x, int y){
    x += y;
    if (x >= Mod) x %= Mod;
}
void sub(int &x, int y){
    x -= y;
    while(x < 0) x += Mod;
}
void mul(int &x, int y){
    x = 1LL * x * y % Mod;
}

void process(void){
    cin >> N >> M;
    for (int i = 0; i < 2 * N; ++i) cnt[i % M]++;
    genFac(2 * N);

    dp[0][0] = 1;
    for (int i = 0; i < M; ++i){
        memset(dp[1], 0, sizeof dp[1]);
        for (int j = 0; j <= N; ++j){
            for (int k = 0; k <= min(j, cnt[i] / 2); ++k){
                int ways = dp[0][j - k];
                mul(ways, fac[cnt[i]]);
                mul(ways, inv[cnt[i] - 2 * k]);
                mul(ways, C(j, k));
                add(dp[1][j], ways);
            }
        }
        swap(dp[0], dp[1]);
    }
    int ans = 0;
    for (int i = 0; i <= N; ++i){
        int ways = dp[0][i];
        mul(ways, C(N, i));
        mul(ways, fac[2 * N - 2 * i]);

        if(i & 1){
            sub(ans, ways);
        }
        else{
            add(ans, ways);
        }
    }
    cout << ans;
}
signed main(){
    #define name "Whisper"
    cin.tie(nullptr) -> sync_with_stdio(false);
    //freopen(name".inp", "r", stdin);
    //freopen(name".out", "w", stdout);
    process();
    return (0 ^ 0);
}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 18 / 18
• Subtask 5: 48 / 48