Submission #154281

#	Time	Username	Problem	Language	Result	Execution time	Memory
154281		karma	Asceticism (JOI18_asceticism)	C++14	100 / 100	15 ms	2040 KiB

asceticism

#include<bits/stdc++.h>
#define Task     "test"
#define ll       long long
#define pb       emplace_back

using namespace std;

const int N = int(1e5) + 5;
const int mod = int(1e9) + 7;

ll f[N], inv[N];
int n, k;

ll Power(ll x, ll y) {
    ll res = 1;
    while(y) {
        if(y & 1) res = res * x % mod;
        x = x * x % mod; y >>= 1;
    }
    return res;
}

int nCk(int n, int k) {return f[n] * inv[k] % mod * inv[n - k] % mod;}

int Eulerian(int n, int k) {
    int res = 0;
    for(int i = 0; i <= k; ++i) {
        if(i & 1) res -= (nCk(n + 1, i) * Power(k + 1 - i, n) % mod);
        else res += (nCk(n + 1, i) * Power(k + 1 - i, n) % mod);
        if(res < 0) res += mod;
        else if(res >= mod) res -= mod;
    }
    return res;
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    if(fopen(Task".inp", "r")) {
        freopen(Task".inp", "r", stdin);
        freopen(Task".out", "w", stdout);
    }
    cin >> n >> k;
    f[0] = 1;
    for(int i = 1; i <= n + 1; ++i) f[i] = f[i - 1] * i % mod;
    inv[n + 1] = Power(f[n + 1], mod - 2);
    for(int i = n; i >= 0; --i) inv[i] = inv[i + 1] * (i + 1) % mod;
    cout << Eulerian(n, k - 1);
}

Compilation message (stderr)

asceticism.cpp: In function 'int main()':
asceticism.cpp:40:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen(Task".inp", "r", stdin);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
asceticism.cpp:41:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen(Task".out", "w", stdout);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 20 / 20
• Subtask 3: 25 / 25
• Subtask 4: 51 / 51