Submission #974076

#	Time	Username	Problem	Language	Result	Execution time	Memory
974076		VinhLuu	Magneti (COCI21_magneti)	C++17	110 / 110	124 ms	8788 KiB

Main

#include <bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define pb push_back
using namespace std;

typedef pair<int,int> pii;
const int N = 1e4 + 5;
const int mod = 1e9 + 7;

int n, l, ft[N], inv[N], f[2][55][N], ans, a[N];

void get(int &x,int y){
    x = (x + y) % mod;
}

int lt(int u,int v){
    if(v == 0) return 1;
    int x = u;
    int kq = 1;
    while(v){
        if(v & 1) kq = kq * x % mod;
        x = x * x % mod;
        v /= 2;
    }
    return kq;
}

void pre(){
    int full = 1e4;
    ft[0] = 1;
    inv[0] = 1;
    for(int i = 1; i <= full; i ++){
        ft[i] = ft[i - 1] * i % mod;
        inv[i] = inv[i - 1] * lt(i, mod - 2) % mod;
    }
}

int C(int u,int v){
    if(u == v || u == 0) return 1;
    return ft[v] * inv[v - u] % mod * inv[u] % mod;
}

void sub1(){
    int d = (n - 1) * a[1] + 1;
    cout << ft[n] * C(n, l - d + n) % mod;
}

signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    #define task "v"
    if(fopen(task ".inp","r")){
        freopen(task ".inp","r",stdin);
        freopen(task ".out","w",stdout);
    }
    pre();
    cin >> n >> l;
    for(int i = 1; i <= n; i ++) cin >> a[i];
    sort(a + 1, a + n + 1);
    if(a[n] == a[1]){
        sub1();
        return 0;
    }
    int pre = 0, nx = 1;
    f[0][0][0] = 1;
    for(int i = 1; i <= n; i ++){
        f[nx][0][0] = 0;
        for(int j = 1; j <= i; j ++){
            for(int k = 1; k <= l; k ++){
                f[nx][j][k] = f[pre][j - 1][k - 1];
                if(k >= a[i]) get(f[nx][j][k], f[pre][j][k - a[i]] * j % mod * 2 % mod);
                if(k >= 2 * a[i] - 1) get(f[nx][j][k], f[pre][j + 1][k - 2 * a[i] + 1] * j % mod * (j + 1) % mod);

//                cout << pre << " " << nx << " " << i << " " << j << " " << k << " " << f[nx][j][k] << " f\n";
            }
        }
        swap(pre, nx);
    }
    for(int i = 1; i <= l; i ++){
//        cout << 1 << " " << i << " " << f[pre][1][i] << " g\n";
        get(ans, f[pre][1][i] * C(n, l - i + n) % mod);
    }
    cout << ans;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:55:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   55 |         freopen(task ".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:56:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   56 |         freopen(task ".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 20 / 20
• Subtask 3: 30 / 30
• Subtask 4: 50 / 50