Submission #1693528

---

Source Code Expand

#include <cstdio>
#include <cstring>
#define MAXN 4010
#define LL long long

const LL P=1000000007;

int n,k;
LL f[MAXN][MAXN],c[MAXN][MAXN],g[MAXN];

void update(LL &x,LL y){ x=(x+y)%P; }

void pre_gao(){
	for(int i=0;i<MAXN;i++){
		c[i][0]=1;
		for(int j=1;j<=i;j++)
			c[i][j]=(c[i-1][j-1]+c[i-1][j])%P;
	}
}

LL gay(int x,int y){
	return c[x+y-1][y];
}

LL gao(){
	f[1][1]=1;
	for(int i=2;i<=k;i++){
		for(int j=1;j<i;j++)
			update(f[i][j+1],f[i-1][j]);
		LL temp=0;
		for(int j=i-1;j>=1;j--){
			update(temp,f[i-1][j]);
			update(f[i][j],temp);
		}
		g[i-1]=temp;
	}
	g[0]=1;
	LL ans=g[k-1];
	for(int i=1;i<=k-1;i++){
		int j=k-1-i;
		if(n-2-j>=i){
			LL temp=c[n-2-j][i];
			if(!j) update(ans,temp);
			else{
				for(int l=1;l<=j;l++)
					update(ans,temp*f[j][l]%P*gay(l+1,i));
			}
		}
	}
	for(int i=1;i<n-k;i++) ans=ans*2%P;
	return ans;
}

int main(){
#ifdef DEBUG
	freopen("F.in","r",stdin);
#endif
	scanf("%d%d",&n,&k);
	pre_gao();
	printf("%lld\n",gao());
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:58:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&n,&k);
                     ^

Judge Result