Submission #1106260

#	Time	Username	Problem	Language	Result	Execution time	Memory
1106260		_rain_	Boat (APIO16_boat)	C++14	100 / 100	1261 ms	6348 KiB

boat

#include<bits/stdc++.h>
using namespace std;
 
typedef long long ll ;
typedef pair<int,int> ii;
#define fi first
#define se second
#define name "main"
 
const int N=(int)500;
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;
	}
vector<int>nen;
vector<ii>line;
int a[N+2],b[N+2],n;
int L[N+2]={},R[N+2]={},f[N*3+2][N+2]={},dp[N+2][N*3+2]={};
int sing[N+2]={},fact[N+2]={},inv[N+2]={},w[N+2]={};
int Combine(int x,int y){
	if (x>y) return 0;
	return (ll)fact[y]*inv[y-x]%MOD*inv[x]%MOD;
}

int C(int k,int n){
	if (k>n) return 0;
	int res=1;
	for(int i=n-k+1;i<=n;++i) res=mul(res,i);
	return mul(res,inv[k]);
}
bool intersec(ii x,int a,int b){
	if (b<x.fi||a>x.se) return false;
	return true;
}
 
void build(){
	memset(L,0x3f,sizeof L);
	memset(R,-0x3f,sizeof R);
	fact[0]=1;
	for(int i=1;i<=N;++i) fact[i]=mul(fact[i-1],i);
	inv[N]=power(fact[N],MOD-2);
	for(int i=N;i>=1;--i) inv[i-1]=mul(inv[i],i);
	for(int id=1;id<=line.size();++id){
		int dodai=line[id-1].se-line[id-1].fi+1;
		for(int j=0;j<=n;++j) w[j]=0;
		w[1]=dodai;
		int tich=dodai;
		for(int j=2;j<=min(dodai,n);++j) {
			tich=mul(tich,dodai-j+1);
			w[j]=mul(tich,inv[j]);
		}
		for(int j=1;j<=n;++j){
			for(int c=1;c<=min(j,dodai);++c)
				f[id][j]=add(f[id][j],mul(Combine(c-1,j-1),w[c]));
		}
	}
	for(int i=1;i<=n;++i){
		for(int j=1;j<=line.size();++j){
			if (intersec(line[j-1],a[i],b[i])) 
				L[i]=min(L[i],j),R[i]=max(R[i],j);
		}
	}
	return;
}
 
int32_t main(){
	ios::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);

	cin>>n;
	for(int i=1;i<=n;++i){
		cin>>a[i]>>b[i];
		nen.push_back(a[i]);
		nen.push_back(b[i]);
		nen.push_back(a[i]-1);
	}
	sort(nen.begin(),nen.end());
	nen.resize(unique(nen.begin(),nen.end())-nen.begin());
	for(int i=1;i<nen.size();++i){
		if (i-1==0) line.push_back({nen[i-1],nen[i]});
		else line.push_back({nen[i-1]+1,nen[i]});
	}
	// cout<<nen.size()<<'\n';
	build();
	for(int i=0;i<=line.size();++i) dp[0][i]=1;
	for(int i=1;i<=n;++i){
		// cout<<i<<'\n';
		for(int id=L[i];id<=R[i];++id){
			int cnt=0;
			pair<int,int> xx=line[id-1];
			if (id==L[i]){
				int dodai=line[id-1].se-a[i]+1;
				for(int j=0;j<=i;++j) sing[j]=0;
				for(int j=1;j<=i;++j) w[j]=C(j,dodai);
				for(int j=1;j<=i;++j){
					for(int c=1;c<=j;++c)
						sing[j]=add(sing[j],mul(Combine(c-1,j-1),w[c]));
				}
				xx={a[i],line[id-1].se};
			}
			for(int j=i;j>=1;--j){
				if (intersec(xx,a[j],b[j])) ++cnt;
				if (id==L[i]) dp[i][id]=add(dp[i][id],mul(sing[cnt],dp[j-1][id-1]));
				else dp[i][id]=add(dp[i][id],mul(f[id][cnt],dp[j-1][id-1]));
			}
		}
		for(int j=L[i];j<=line.size();++j) dp[i][j]=add(dp[i][j],dp[i][j-1]);
	}
	int ans=0;
	for(int i=1;i<=n;++i) ans=add(ans,dp[i][line.size()]);
	cout<<ans;
	exit(0);
}

Compilation message (stderr)

boat.cpp: In function 'void build()':
boat.cpp:55:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 |  for(int id=1;id<=line.size();++id){
      |               ~~^~~~~~~~~~~~~
boat.cpp:70:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   70 |   for(int j=1;j<=line.size();++j){
      |               ~^~~~~~~~~~~~~
boat.cpp: In function 'int32_t main()':
boat.cpp:91:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   91 |  for(int i=1;i<nen.size();++i){
      |              ~^~~~~~~~~~~
boat.cpp:97:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   97 |  for(int i=0;i<=line.size();++i) dp[0][i]=1;
      |              ~^~~~~~~~~~~~~
boat.cpp:119:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  119 |   for(int j=L[i];j<=line.size();++j) dp[i][j]=add(dp[i][j],dp[i][j-1]);
      |                  ~^~~~~~~~~~~~~

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