Submission #142986

#	Time	Username	Problem	Language	Result	Execution time	Memory
142986		IC_COLDSTOP	Boat (APIO16_boat)	C++17	100 / 100	696 ms	12536 KiB

boat

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define int ll
#define MP make_pair
#define pb push_back
#define F first
#define S second
#define pii pair<int,int>
#define REP(i,a,b) for(int i=a; i<b; i++)

const int MX=5e2+3, mod=1e9+7;

int n, m, dp[10][MX*2][2*MX], l[MX], r[MX], num[2*MX], p[MX*2];
map<int,int> mark;
vector<int> vec;

int pw(int a, int b){
	if(!b) return 1;
	int nsf=pw(a,b/2);
	nsf=nsf*nsf%mod;
	if(b&1) nsf*=a;
	return nsf%mod;
}

int32_t main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	REP(i,1,MX*2) p[i]=pw(i,mod-2);
	cin>>n;
	REP(i,0,n){
		cin>>l[i]>>r[i];
		r[i]++;
		if(!mark[l[i]]) mark[l[i]]=1, vec.pb(l[i]);
		if(!mark[r[i]]) mark[r[i]]=1, vec.pb(r[i]);
	}
	m=vec.size();
	//cout<<m<<endl;
	sort(vec.begin(), vec.end());
	int mm=0;
	dp[mm][0][0]=1;
	REP(j,1,m){
		dp[mm][j][0]=dp[mm][j-1][0]+dp[mm][j-1][1];
		if(l[0]<vec[j] && r[0]>=vec[j]) dp[mm][j][1]=(vec[j]-vec[j-1])%mod, num[j]++;
	//	cout<<j<<" "<<dp[mm][j][0]<<" "<<dp[mm][j][1]<<" "<<vec[j]<<" "<<vec[j-1]<<endl;
	}
	REP(i,1,n){
		mm^=1;
		REP(j,1,m){
			dp[mm][j][0]=0;
			if(j>1) REP(w,0,num[j-1]+1){
				dp[mm][j][0]=(dp[mm][j-1][w]+dp[mm][j][0])%mod;
			//	if(i==2 && j==2) cout<<" B "<<dp[mm][j][0]<<" "<<dp[mm][j-1][w]<<endl;
			}
			else dp[mm][j][0]=1;
			int flg=0, cnt=vec[j]-vec[j-1];
			if(l[i]<vec[j] && r[i]>=vec[j]) flg=1, num[j]++;
			REP(w,1,num[j]+1){
				dp[mm][j][w]=dp[mm^1][j][w];
				if(flg){
					dp[mm][j][w]=((ll)dp[mm][j][w] +  (ll)dp[mm^1][j][w-1]  *  (cnt-w+1) %mod  *  p[w]%mod )%mod;
				}
			}
			//cout<<i<<" "<<j<<" "<<flg<<" "<<num[j]<<endl;
		}
	}
	//cout<<endl;
	int sum=0;
	REP(w,0,MX*2){
		sum=(sum+dp[mm][m-1][w])%mod;
		//cout<<w<<" "<<dp[mm][m-1][w]<<" "<<dp[mm][m-2][w]<<" "<<dp[mm][m-3][w]<<" "<<dp[mm^1][m-1][w]<<" "<<dp[mm^1][m-2][w]<<" "<<dp[mm^1][m-3][w]<<endl;
	}
	cout<<sum-1<<endl;
	return 0;
}

• Subtask 1: 9 / 9
• Subtask 2: 22 / 22
• Subtask 3: 27 / 27
• Subtask 4: 42 / 42