Submission #1181667

#	Time	Username	Problem	Language	Result	Execution time	Memory
1181667		Alish	Asceticism (JOI18_asceticism)	C++20	100 / 100	7 ms	1864 KiB

asceticism

#include<bits/stdc++.h>

using namespace std;

typedef long long int	ll;
typedef pair<int, int>	pii;
typedef pair<ll, ll>	pll;
typedef long double     ld;


#define F		        first
#define S		        second
#define pb		        push_back
#define endl            '\n'
#define Mp              make_pair
#define all(x)          x.begin(), x.end()
#define debug(x)        cerr << #x << " = " << x << endl;
#define fast_io         ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io         freopen("input19.txt" , "r" , stdin) ;

const ll mod=1e9+7;
const int N = 1e5+23;

ll fact[N], inv[N];
int n, k;

ll power(ll a, ll b){
    ll ans=1;
    while(b){
        if(b&1) ans=ans*a%mod;
        b>>=1;
        a=a*a%mod;
    }
    return ans;
}

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

int main()
{
    fast_io
    cin>>n>>k;
    fact[0]=1;
    for (int i=1; i<N; i++) fact[i]=fact[i-1]*i%mod;
    inv[N-1]=power(fact[N-1], mod-2);
    for (int i=N-2; i>=0; i--) inv[i]=inv[i+1]*(i+1)%mod;

    ll ans=0;
    for(int i=0; i<k; i++){
        if(i&1) ans=(ans-C(i, n+1)*power(k-i, n)%mod+mod)%mod;
        else ans=(ans+C(i, n+1)*power(k-i, n)%mod)%mod;
    }
    cout<<ans<<endl;

}

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