Submission #956865

#	Time	Username	Problem	Language	Result	Execution time	Memory
956865		LCJLY	Tents (JOI18_tents)	C++14	100 / 100	186 ms	71308 KiB

tents

#include <bits/stdc++.h>
using namespace std;	
 
#define int long long 
#define ld long double
#define show(x,y) cout << y << " " << #x << endl;
#define show2(x,y,i,j) cout << y << " " << #x << "  " << j << " " << #i << endl;
#define show3(x,y,i,j,p,q) cout << y << " " << #x << "  " << j << " " << #i << "  " << q << " " << #p << endl;
#define show4(x,y) for(auto it:y) cout << it << " "; cout << #x << endl;
typedef pair<long long,int>pii;
typedef pair<pii,pii>pi2;
mt19937 rng(chrono::system_clock::now().time_since_epoch().count());

const int mod=1e9+7;
int memo[3005][3005];

int f(int n){
	int hold=n*(n-1)/2;
	hold=(hold+mod)%mod;
	//show2(n,n,hold,hold);
	return hold;
}

int dp(int a, int b){
	if(a==0||b==0) return 1;
	if(a<0||b<0) return 0;
	if(memo[a][b]!=-1) return memo[a][b];
	
	int ans=0;
	
	ans=(ans+dp(a-1,b));
	if(a>=2&&b>=1){
		int hold=dp(a-2,b-1)*(a-1)*b;
		hold%=mod;
		ans=(ans+hold)%mod;
	}
	if(a>=1&&b>=2){
		int hold=dp(a-1,b-2)*f(b);
		hold%=mod;
		ans=(ans+hold)%mod;
	}
	if(a>=1&&b>=1){
		int hold=dp(a-1,b-1)*4*b;
		hold%=mod;
		ans=(ans+hold)%mod;
	}
	return memo[a][b]=ans;
}

void solve(){
	int n,k;
	cin >> n >> k;
	
	memset(memo,-1,sizeof(memo));
	cout << dp(n,k)-1;
	
}
 
int32_t main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	int t=1;
	//freopen("in.txt","w",stdout);
	//cin >> t;
	while(t--){
		solve();
	}
}

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