Submission #27465461

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Source Code Expand

#include<bits/stdc++.h>
#define P 1000000007
#define N 2005

inline void fmo(int &x){
	x+=(x>>31)&P;
}
inline int fp(int x,int k=P-2){
	int res=1;
	for(;k;k>>=1,x=1ll*x*x%P)
		if(k&1)
			res=1ll*res*x%P;
	return res;
}

int fac[N*N],inv[N*N],ifac[N*N];
inline void init(int x){
	fac[0]=1;
	for(int i=1;i<=x;i++)
		fac[i]=1ll*fac[i-1]*i%P;
	inv[1]=1;
	for(int i=2;i<=x;i++)
		fmo(inv[i]=-1ll*P/i*inv[P%i]%P);
	ifac[0]=1;
	for(int i=1;i<=x;i++)
		ifac[i]=1ll*ifac[i-1]*inv[i]%P;
}
inline int C(int x,int y){
	if(x<0||y<0||x<y)
		return 0;
	return 1ll*fac[x]*ifac[y]%P*ifac[x-y]%P;
}

int n,k;

int f[N][N];

int main(){
	scanf("%d%d",&n,&k);
	if(k==1)
		return puts("1"),0;
	init(n*k);
	f[0][0]=1;
	for(int i=0;i<=n;i++)
		for(int j=0;j<=n;j++) if(f[i][j]){
			if(j<n)
				fmo(f[i][j+1]+=f[i][j]-P);
			if(i<n&&j)
				fmo(f[i+1][j-1]+=1ll*C((n-i)*k-j-1,k-2)*f[i][j]%P-P);
		}
	printf("%d\n",(int)(1ll*f[n][0]*fac[n]%P));
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:39:7: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   39 |  scanf("%d%d",&n,&k);
      |  ~~~~~^~~~~~~~~~~~~~

Judge Result