Submission #595284

#	Time	Username	Problem	Language	Result	Execution time	Memory
595284		Koosha_mv	Ruins 3 (JOI20_ruins3)	C++14	100 / 100	1692 ms	18996 KiB

ruins3

#include <bits/stdc++.h>
using namespace std;
#define dbgv(v) cout<<#v<<" = "; f(i,0,v.size()) cout<<v[i]<<" "; cout<<endl
#define dbga(a,x,y) cout<<#a<<" = "; f(i,x,y) cout<<a[i]<<" "; cout<<endl
#define erorp(x) cout<<#x<<"={"<<x.F<<" , "<<x.S<<"}"<<endl
#define eror(x) cout<<#x<<'='<<(x)<<endl
#define f_(i,a,b) for(int i=a;i>=b;i--)
#define f(i,a,b) for(int i=a;i<b;i++)
#define nb(x) __builtin_popcount(x)
#define all(v) v.begin(),v.end()
#define bit(n,k) (((n)>>(k))&1)
#define Add(x,y) x=(x+y)%mod
#define maxm(a,b) a=max(a,b)
#define minm(a,b) a=min(a,b)
#define lst(x) x[x.size()-1]
#define sz(x) int(x.size())
#define mp make_pair
#define ll long long
#define pb push_back
#define S second
#define F first
#define int ll

const int N=1205,mod=1e9+7,inv2=mod/2+1;

int n,t,f[N],g[N],fact[N],ps[N][N],C[N][N],dp[N][N],mark[N];
vector<int> A,B;

ll pow(ll x,ll y,ll mod){return(!y?1:pow(x*x%mod,y/2,mod)*(y&1?x:1))%mod;}

int G(int n){
	if(n==0) return 1;
	return (C[n][2*n]-C[n-1][2*n]+mod)%mod;
}
int c(int k,int n){
	if(k<0 || k>n) return 0;
	return C[k][n];
}

int32_t main(){
	ios:: sync_with_stdio(0), cin.tie(0), cout.tie(0);
	fact[0]=1;
	f(i,0,N){
		C[0][i]=1;
		f(j,1,i+1) C[j][i]=(C[j-1][i-1]+C[j][i-1])%mod;
		if(i>0) fact[i]=1ll*fact[i-1]*i%mod;
	}
	g[1]=f[1]=1;
	f(i,2,N){
		f(j,0,i/2+1){
			int res=1ll*C[2*j][i]*G(j)%mod*pow(inv2,2*j,mod)%mod;
			res=1ll*res*fact[i]%mod*fact[i]%mod;
			Add(g[i],res);
		}
		f[i]=g[i];
		f(j,1,i){
			Add(f[i],mod-1ll*f[j]*g[i-j]%mod*C[j][i]%mod*C[j-1][i-1]%mod);
		}
	}
	cin>>n;
	f(i,1,n+1){
		int x;
		cin>>x;
		mark[x]=1;
	}
	f(i,1,2*n+1){
		if(mark[i]) A.pb(i);
		else B.pb(i);
	}
	dp[0][0]=1;
	f(i,0,n+1) ps[0][i]=1;
	f(i,1,n+1){
		f(j,1,i+1){
			f(k,0,i){
				int x=lower_bound(all(B),A[j-1])-B.begin()-k;
				int res=1ll*ps[k][j-1]*c(i-k-1,(n+1-j)-(n-i)-1)%mod*f[i-k]%mod;
				res=1ll*res*c(i-k,x)%mod;
				Add(dp[i][j],res);
				}
			}
		f(j,1,n+1) ps[i][j]=(ps[i][j-1]+dp[i][j])%mod;
	}
	int ans=0;
	f(i,1,n+1) Add(ans,dp[n][i]);
	cout<<ans;
}

• Subtask 1: 6 / 6
• Subtask 2: 52 / 52
• Subtask 3: 42 / 42