Submission #1029618

#	Time	Username	Problem	Language	Result	Execution time	Memory
1029618		atom	Magneti (COCI21_magneti)	C++17	10 / 110	1 ms	856 KiB

Main

#include "bits/stdc++.h"
// @JASPER'S BOILERPLATE
using namespace std;
using ll = long long;

#ifdef JASPER
#include "debug.h"
#else
#define debug(...) 166
#endif

const int MOD = 1e9 + 7;
const int N = 2e4 + 5;

int bPow(int a, int b) {
    ll ans = 1;
    while (b) {
        if (b & 1) ans = (1LL * ans * a)  % MOD;
        a = (1LL * a * a) % MOD;
        b >>= 1;
    }
    return ans;
}

int fac[N], inv[N];

void prepare() {
    fac[0] = 1;
    for (int i = 1; i < N; ++i)
        fac[i] = (1LL * fac[i - 1] * i) % MOD;

    inv[N - 1] = bPow(fac[N - 1], MOD - 2);
    for (int i = N - 2; i >= 0; --i)
        inv[i] = (1LL * inv[i + 1] * (i + 1)) % MOD;
}

int C(int k, int n) {
    if (k > n) return 0;
    return ((1LL * fac[n] * inv[n - k]) % MOD * (inv[k])) % MOD;
}

signed main() {
    cin.tie(0) -> sync_with_stdio(0);
    
    #ifdef JASPER
        freopen("in1", "r", stdin);
    #endif

    prepare();

    int n, l;
    cin >> n >> l;
    vector <int> a(n + 1);
    for (int i = 1; i <= n; ++i) cin >> a[i];

    sort(a.begin(), a.end());
    if (a[1] == a[n]) {
        // sub1
        int p = (n - 1) * a[1] + 1;
        ll ans = (1LL * fac[n] * C(n, n + l - p)) % MOD;      
        cout << ans << "\n";  
    }
    
    return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 0 / 20
• Subtask 3: 0 / 30
• Subtask 4: 0 / 50