Submission #33346584

---

Source Code Expand

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const LL mod=998244353;
const int N=3e5+5;
LL n,k,ans;
LL fac[N],inv[N];
LL prod[N]; //从K 往前 i 个数的连乘  
LL qwqmi(LL x,LL b)
{
	LL res=1;
	while(b)
	{
		if(b&1) res=res*x%mod;
		x=x*x%mod;
		b>>=1;
	}
	return res%mod;
}
void preprocess()
{
	fac[0]=inv[0]=1;
	for(int i=1;i<N;i++)
		fac[i]=fac[i-1]*i%mod;
	inv[N-1]=qwqmi(fac[N-1],mod-2);
	for(int i=N-2;i>=1;i--)
		inv[i]=inv[i+1]*(i+1)%mod;
}
int main()
{
	preprocess();
	scanf("%lld%lld",&n,&k);
	prod[0]=1;
	for(LL i=1;i<N;i++)
		prod[i]=prod[i-1]*((k-i+2)%mod)%mod;
	for(int i=0;i<=min(n,k);i++)
	{
		LL twomi=qwqmi(2,i);
		LL w1=fac[n]*inv[i]%mod*inv[n-i]%mod;
		LL w2=inv[i+1]*prod[i+1]%mod;
		LL res=twomi*w1%mod*w2%mod;
		ans+=res;
		ans%=mod;
	}
	printf("%lld\n",ans);
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:32:7: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   32 |  scanf("%lld%lld",&n,&k);
      |  ~~~~~^~~~~~~~~~~~~~~~~~

Judge Result