Submission #205185

#	Time	Username	Problem	Language	Result	Execution time	Memory
205185		Atill83	Asceticism (JOI18_asceticism)	C++14	100 / 100	31 ms	2040 KiB

asceticism

#include <bits/stdc++.h>
#define ff first
#define ss second
#define endl '\n'
using namespace std;
const long long INF = (long long) 1e18;
const int mod = (int) 1e9+7;
const int MAXN = (int) 1e5+5;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
int n, k;
int dp[MAXN];
ll fact[MAXN];
ll inv[MAXN];

ll bp(ll a, ll b){
    ll res = 1;
    while(b){
        if(b % 2) res = (res * a) % mod;
        a = (a * a) % mod;
        b = b / 2;
    }
    return res;
}

ll comb(ll a, ll b){
    return fact[a]*inv[b]%mod*inv[a - b]%mod;
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);cout.tie(nullptr);

    #ifdef Local
        freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/int.txt","r",stdin);
        freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/out.txt","w",stdout);
    #endif

    cin>>n>>k;
    fact[0] = 1;
    inv[0] = 1;
    for(int i = 1;  i <= n + 10; i++){
        fact[i] = fact[i - 1]* i % mod;
        inv[i] = bp(fact[i], mod - 2);
    }
    ll ans = 0;
    for(int i = 0; i < k; i++){
        ans += (i % 2 ? -1: 1)*(comb(n + 1, i)*bp((k - i), n)%mod);
        ans += mod;
        ans %= mod;
    }
    cout<<ans<<endl;

    #ifdef Local
        cout<<endl<<fixed<<setprecision(2)<<1000.0 * clock() / CLOCKS_PER_SEC<< " milliseconds ";
    #endif
}

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