Submission #1026740

#	Time	Username	Problem	Language	Result	Execution time	Memory
1026740		BABY_GANGSTER	Asceticism (JOI18_asceticism)	C++14	100 / 100	8 ms	2136 KiB

asceticism

#include<bits/stdc++.h>
#define ll long long
#define pll pair<ll, ll>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define ld long double
#define sz(a) ((ll)(a).size())
using namespace std;
 
const ll maxn=100005, Mod=1e9+7;
ll po[maxn], inv[maxn];
ll C(ll k, ll n){return po[n]*inv[k]%Mod*inv[n-k]%Mod;}
 
ll binpow(ll a, ll k)
{
    ll ans=1;
    for (; k; a=a*a%Mod, k>>=1)
        if (k&1) ans=ans*a%Mod;
    return ans;
}
 
 
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    ll n, k; cin >> n >> k;
    for (ll i=0; i<maxn; i++)
        po[i]=i?po[i-1]*i%Mod:1;
    inv[maxn-1]=binpow(po[maxn-1], Mod-2);
    for (ll i=maxn-2; i>=0; i--)
        inv[i]=inv[i+1]*(i+1)%Mod;
    ll ans=0;
    for (ll i=0; i<k; i++)
        ans+=(i&1?-1:1)*C(i, n+1)*binpow(k-i, n)%Mod;
    cout << (ans%Mod+Mod)%Mod;
}

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