Submission #338805

#	Time	Username	Problem	Language	Result	Execution time	Memory
338805		alishahali1382	Asceticism (JOI18_asceticism)	C++14	100 / 100	11 ms	1920 KiB

asceticism

#include <bits/stdc++.h>
#pragma GCC optimize ("O2,unroll-loops")
//#pragma GCC optimize("no-stack-protector,fast-math")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<pii, int> piii;
typedef pair<ll, ll> pll;
#define debug(x) cerr<<#x<<'='<<(x)<<endl;
#define debugp(x) cerr<<#x<<"= {"<<(x.first)<<", "<<(x.second)<<"}"<<endl;
#define debug2(x, y) cerr<<"{"<<#x<<", "<<#y<<"} = {"<<(x)<<", "<<(y)<<"}"<<endl;
#define debugv(v) {cerr<<#v<<" : ";for (auto x:v) cerr<<x<<' ';cerr<<endl;}
#define all(x) x.begin(), x.end()
#define pb push_back
#define kill(x) return cout<<x<<'\n', 0;

const int inf=1000000010;
const ll INF=10000000000000010LL;
const int mod=1000000007;
const int MAXN=100010;

ll n, m, k, u, v, x, y, t, a, b, ans;
ll F[MAXN], I[MAXN];

ll powmod(ll a, ll b){
	ll res=1;
	for (; b; b>>=1, a=a*a%mod) if (b&1) res=res*a%mod;
	return res;
}
ll nCr(ll n, ll r){
	if (r<0 || r>n) return 0;
	return F[n]*I[r]%mod*I[n-r]%mod;
}

int main(){
	ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	//freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
	F[0]=1;
	for (int i=1; i<MAXN; i++) F[i]=F[i-1]*i%mod;
	I[MAXN-1]=powmod(F[MAXN-1], mod-2);
	for (int i=MAXN-1; i; i--) I[i-1]=I[i]*i%mod;
	cin>>n>>k;
	for (int ij=0; ij<=k; ij++){
		ll res=nCr(n+1, ij);
//		for (int i=0; i<=ij; i++) res=(res + nCr(n-k+i, i)*nCr(k-i, ij-i))%mod;
		res=res*powmod(k-ij, n)%mod;
		if (ij&1) res*=-1;
		ans=(ans + res)%mod;
	}
//	debug(ans)
	if (ans<0) ans+=mod;
	cout<<ans<<"\n";
	
	return 0;
}

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