Submission #49058

#	Time	Username	Problem	Language	Result	Execution time	Memory
49058		Namnamseo	Asceticism (JOI18_asceticism)	C++17	100 / 100	49 ms	2572 KiB

asceticism

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pp;
typedef pair<ll,ll> pll;
void read(int& x){ scanf("%d",&x); }
void read(ll& x){ scanf("%lld",&x); }
template<typename T,typename... Args>
void read(T& a,Args&... b){ read(a); read(b...); }
#define all(x) (x).begin(),(x).end()
#define pb push_back
#define eb emplace_back
#define x first
#define y second

int n, k;
const ll mod = 1'000'000'007;

ll fact[200001];

ll Pow(ll b, ll e){
	ll ret=1;
	while(e){
		if(e&1) (ret*=b)%=mod;
		e/=2; (b*=b)%=mod;
	}
	return ret;
}

ll Comb(ll n, ll r){
	if(r<0 || r>n) return 0;
	return fact[n]*Pow(fact[r], mod-2)%mod*Pow(fact[n-r], mod-2)%mod;
}

int main()
{
	fact[0]=1; for(int i=1; i<=200000; ++i) fact[i]=fact[i-1]*i%mod;
	
	int n, k;
	cin >> n >> k; --k;
	ll ans = 0;
	for(int j=0; j<=k; ++j){
		(ans += ((j%2?-1:1)*Comb(n+1, j)*Pow(k-j+1, n)%mod+mod)%mod) %= mod;
	}
	cout << ans;
	return 0;
}

Compilation message (stderr)

asceticism.cpp: In function 'void read(int&)':
asceticism.cpp:6:25: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 void read(int& x){ scanf("%d",&x); }
                    ~~~~~^~~~~~~~~
asceticism.cpp: In function 'void read(ll&)':
asceticism.cpp:7:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 void read(ll& x){ scanf("%lld",&x); }
                   ~~~~~^~~~~~~~~~~

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