Submission #699786

#	Time	Username	Problem	Language	Result	Execution time	Memory
699786		cig32	Asceticism (JOI18_asceticism)	C++17	100 / 100	52 ms	1108 KiB

asceticism

#include "bits/stdc++.h"
using namespace std;
#define int long long
const int MAXN = 2e5 + 10;
const int MOD = 1e9 + 7;
mt19937_64 rng((int)std::chrono::steady_clock::now().time_since_epoch().count());
int rnd(int x, int y) {
  int u = uniform_int_distribution<int>(x, y)(rng); return u;
}
int bm(int b, int p) {
  if(p==0) return 1 % MOD;
  int r = bm(b, p >> 1);
  if(p&1) return (((r*r) % MOD) * b) % MOD;
  return (r*r) % MOD;
}
int inv(int b) { 
  return bm(b, MOD-2);
}
int fastlog(int x) {
  return (x == 0 ? -1 : 64 - __builtin_clzll(x) - 1);
}
void printcase(int i) { cout << "Case #" << i << ": "; }

int fac[MAXN];
int ncr(int n, int r) {
  int b = fac[n] * inv(fac[r]);
  b %= MOD;
  b *= inv(fac[n-r]);
  b %= MOD;
  return b;
}
void solve(int tc) {
  // Wtf eulerian numbers
  // In arvindf232's language - "uninteresting" and "standard"
  // Copy wiki and dump into oeis
  int n;
  cin >> n;
  int k;
  cin >> k;
  fac[0] = 1;
  for(int i=1; i<=n+1; i++) {
    fac[i] = (fac[i-1] * i) % MOD;
  }
  int ans = 0;
  for(int i=0; i<=k; i++) {
    int u = 1;
    if(i&1) u = MOD-1;
    u *= ncr(n+1, i);
    u %= MOD;
    u *= bm(k-i, n);
    u %= MOD;
    ans += u;
    ans %= MOD;
  }
  cout << ans << "\n";
}

int32_t main() {
  ios::sync_with_stdio(0); cin.tie(0);
  int t = 1; //cin >> t;
  for(int i=1; i<=t; i++) solve(i);
}

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