Submission #62462

#	Time	Username	Problem	Language	Result	Execution time	Memory
62462		gusfring	Asceticism (JOI18_asceticism)	C++14	100 / 100	37 ms	2396 KiB

asceticism

# include <bits/stdc++.h>

using namespace std;

const long long mod = 1e9 + 7;
const long long N = 1e5 + 2;

long long binpow(long long a, long long n){
  long long res = 1;
  while(n){
    if(n & 1)
          res = (res * a) % mod;
    a = (a * a) % mod;
    n >>= 1;
  }
  return res;
}

long long n, k, f[N], fi[N];

long long cnk(long long n, long long k){
  return ((f[n] * fi[n - k]) % mod * fi[k]) % mod;
}


int main(){
  f[0] = 1;
  fi[0] = binpow(f[0], mod - 2);
  for(long long i = 1; i < N; i ++){
    f[i] = (f[i - 1] * i) % mod;
    fi[i] = binpow(f[i], mod - 2);
  }
  scanf("%lld %lld", &n, &k);
  long long ans = 0;
  for(long long i = 0; i <= k; i ++){
	  if(i & 1){
	    ans -= (cnk(n + 1, i) * binpow(k - i, n)) % mod;
	    if(ans < 0) ans += mod;
	  }
		else {
	    ans += (cnk(n + 1, i) * binpow(k - i, n)) % mod;
	    if(ans > mod) ans -= mod;
	  }
  }
	printf("%lld\n", ans);
	return 0;
}

Compilation message (stderr)

asceticism.cpp: In function 'int main()':
asceticism.cpp:33:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld %lld", &n, &k);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~

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