Submission #389092

#	Time	Username	Problem	Language	Result	Execution time	Memory
389092		denkendoemeer	Asceticism (JOI18_asceticism)	C++14	100 / 100	16 ms	1872 KiB

asceticism

#include<bits/stdc++.h>
#define ll long long
const int inf=1e9;
#define mod 1000000007
using namespace std;
int fact[200005],inv[200005];
int po(int b,int e)
{
    int p=1;
    while(e){
        if (e%2==1)
            p=1LL*p*b%mod;
        b=1LL*b*b%mod;
        e=e/2;
    }
    return p;
}
int comb(int n,int k)
{
    return 1LL*fact[n]*inv[k]%mod*inv[n-k]%mod;
}
int calc(int n,int k)
{
    if (k>n)
        return 0;
    int ans=0,i;
    for(i=0;i<=k;i++){
        int aux=1LL*comb(n+1,i)*po(k+1-i,n)%mod;
        if (i%2==1)
            ans=(ans-aux+mod)%mod;
        else
            ans=(ans+aux)%mod;
    }
    return ans;
}
int main()
{
    //freopen(".in","r",stdin);
    //freopen(".out","w",stdout);
    int n,k,i;
    fact[0]=1;
    for(i=1;i<=200000;i++)
        fact[i]=1LL*fact[i-1]*i%mod;
    inv[200000]=po(fact[200000],mod-2);
    for(i=199999;i>=0;i--)
        inv[i]=1LL*inv[i+1]*(i+1)%mod;
    scanf("%d%d",&n,&k);
    printf("%d\n",calc(n,k-1));
return 0;
}

Compilation message (stderr)

asceticism.cpp: In function 'int main()':
asceticism.cpp:47:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   47 |     scanf("%d%d",&n,&k);
      |     ~~~~~^~~~~~~~~~~~~~

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