Submission #1227946

#	Time	Username	Problem	Language	Result	Execution time	Memory
1227946		_rain_	Tents (JOI18_tents)	C++20	48 / 100	2093 ms	328 KiB

tents

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;

const int MOD=(int)1e9+7;
	int add(int a,int b){
		return a+b>=MOD?a+b-MOD:a+b;
	}
	int sub(int a,int b){
		return a-b<0?a-b+MOD:a-b;
	}
	int mul(int a,int b){
		return (LL)a*b%MOD;
	}
	int power(int a,int b){
		int res=1;
		for(;b;b>>=1,a=mul(a,a)){
			if (b&1) res=mul(res,a);
		}
		return res;
	}
	
	
const int N=(int)3000;
	int fac[N+2] , inv[N+2];
	int ff[N*2+2]={};
	
	void build(){
		fac[0]=1;
		for(int i=1;i<=N;++i) fac[i]=mul(fac[i-1],i);
		inv[N]=power(fac[N],MOD-2);
		for(int i=N;i>=1;--i) inv[i-1]=mul(inv[i],i);
		ff[0]=1;
		for(int i=2;i<=N*2;i+=2) ff[i]=mul(ff[i-2],i-1);
		return;
	}
	int C(int x,int y){
		if (x>y) return 0;
		return (LL)fac[y]*inv[y-x]%MOD*inv[x]%MOD;
	}
	
	int numrow,numcol;

int ans2(int a,int b){
	int ans=0;
	for(int i=0;i<=N && i*2<=a;++i){
		for(int j=0;j<=N && j*2<=b;++j){
			if (i*2+j>a||j*2+i>b) continue;
			int addmore=1;
			addmore=mul(addmore,C(i*2+j,a));
			addmore=mul(addmore,C(j*2+i,b));
			addmore=mul(addmore,C(j,i*2+j));
			addmore=mul(addmore,C(i,j*2+i));
			addmore=mul(addmore,fac[i]) , addmore=mul(addmore,fac[j]);
			addmore=mul(addmore,ff[2*i]) , addmore=mul(addmore,ff[2*j]);
			ans=add(ans,addmore);
		}
	}
	return ans;
}
int calc(int a,int b){
	int ans=0;
	for(int i=0;i<=min(a,b);++i){
		int addmore=power(4,i);
		addmore=mul(addmore,C(i,a));
		addmore=mul(addmore,C(i,b));
		addmore=mul(addmore,ans2(a-i,b-i));
		addmore=mul(addmore,fac[i]);
		ans=add(ans,addmore);
	}
	return ans;
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0) ; cout.tie(0);
	#define task "main"
	if (fopen(task".inp","r")){
		freopen(task".inp","r",stdin);
		freopen(task".out","w",stdout);
	}
	
	cin>>numrow>>numcol;
	build();
	cout<<sub(calc(numrow,numcol),1);
	
	return 0;
}

Compilation message (stderr)

tents.cpp: In function 'int main()':
tents.cpp:79:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   79 |                 freopen(task".inp","r",stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
tents.cpp:80:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |                 freopen(task".out","w",stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 48 / 48
• Subtask 2: 0 / 52