Submission #414115

#	Time	Username	Problem	Language	Result	Execution time	Memory
414115		jamezzz	Asceticism (JOI18_asceticism)	C++14	100 / 100	47 ms	1916 KiB

asceticism

#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#include <ext/rope>
using namespace __gnu_cxx;

typedef tree<long long, null_type, less<long long>,
rb_tree_tag, tree_order_statistics_node_update> pbds;
//less_equal for identical elements

//#define DEBUG

#ifdef DEBUG
#define debug(...) printf(__VA_ARGS__);
#else
#define debug(...)
#endif
#define sf scanf
#define pf printf
#define fi first
#define se second
#define pb emplace_back
#define sz(x) (int)x.size()
#define mnto(x,y) x=min(x,(__typeof__(x))y)
#define mxto(x,y) x=max(x,(__typeof__(x))y)
#define INF 1023456789
#define LINF 1023456789123456789
#define all(x) x.begin(), x.end()
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<int, int> ii;
typedef tuple<int, int, int> iii;
typedef tuple<int, int, int, int> iiii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<pll> vll;

#define mod 1000000007

int n,k;
ll fac[100005],ifac[100005];

ll pwr(int x,int p){
	if(p==0)return 1;
	ll t=pwr(x,p/2);
	ll r=(t*t)%mod;
	if(p%2)r*=x,r%=mod;
	return r;
}

int main(){
	sf("%d%d",&n,&k);k=n-k;
	fac[0]=1;for(int i=1;i<=n+1;++i)fac[i]=(fac[i-1]*i)%mod;
	for(int i=0;i<=n+1;++i)ifac[i]=pwr(fac[i],mod-2);
	ll res=0;
	for(int i=0;i<=k+1;++i){
		ll a=(((fac[n+1]*ifac[i])%mod)*ifac[n+1-i])%mod;
		ll b=pwr(k+1-i,n);
		if(i%2==0)res+=a*b,res%=mod;
		else res+=mod-a*b,res%=mod;
	}
	pf("%lld\n",res);
}

//lol https://en.wikipedia.org/wiki/Eulerian_number

Compilation message (stderr)

asceticism.cpp: In function 'int main()':
asceticism.cpp:55:4: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   55 |  sf("%d%d",&n,&k);k=n-k;
      |    ^

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