Submission #206219

#	Time	Username	Problem	Language	Result	Execution time	Memory
206219		mraron	Boat (APIO16_boat)	C++14	0 / 100	24 ms	12664 KiB

boat

#include<iostream>
#include<vector>
#include<map>
#include<set>
#include<cassert>
#include<cassert>
#include<unordered_map>
#include<unordered_set>
#include<functional>
#include<queue>
#include<stack>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<sstream>
#include<iomanip>
#include<cstdio>
#include<cstdlib>
#include<numeric>
#include<random>
#include<chrono>
#include<bitset>
using namespace std;

#define all(x) (x).begin(), (x).end()
#define pb push_back
#define xx first
#define yy second
#define sz(x) (int)(x).size()
#define gc getchar
#define IO ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define mp make_pair

#ifndef ONLINE_JUDGE
#  define LOG(x) (cerr << #x << " = " << (x) << endl)
#else
#  define LOG(x) ((void)0)
#endif

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

const double PI=3.1415926535897932384626433832795;
const ll INF = 1LL<<62;
const ll MINF = -1LL<<62;

template<typename T> T getint() {
	T val=0;
	char c;
	
	bool neg=false;
	while((c=gc()) && !(c>='0' && c<='9')) {
		neg|=c=='-';
	}

	do {
		val=(val*10)+c-'0';
	} while((c=gc()) && (c>='0' && c<='9'));

	return val*(neg?-1:1);
}

//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count()); uniform_int_distribution<int>(0, n-1)(rng)


int n;
vector<int> lst;
int a[501], b[501];
int ways[1001][1001];
map<int,int> conv;
map<int,int> iconv;

const ll mod=1e9+7;
ll dp[501][1001];
ll fakt[1001];
ll ifakt[1001];

ll fp(ll a, ll b) {
	if(b==0) return 1;
	ll fele=fp(a,b/2);
	ll ans=fele*fele%mod;
	if(b&1) ans=ans*a%mod;
	return ans;
}

ll pascal[1001][1001];

ll choose(ll a, ll b) {
	if(b<0) return 0;
	if(a<b) return 0;
	return fakt[a]*ifakt[b]%mod*ifakt[a-b]%mod+choose(a,b-1);
}

ll calc(int i, int j) {
	if(j<=0) return 0;
	if(dp[i][j]!=-1) return dp[i][j];
	if(j<a[i]) return 0;
	ll ans=(calc(i, j-1)+ways[j-1][j])%mod;
	for(int k=i-1;k>=0;--k) {
		ans=(ans+calc(k,j-1)*choose(ways[j-1][j], i-k-1)%mod);
	}
	return dp[i][j]=ans;
}

int main() {
	IO;
	fakt[0]=1;
	for(int i=1;i<1001;++i) {
		fakt[i]=fakt[i-1]*i%mod;
		ifakt[i]=fp(fakt[i], mod-2);
	}
	pascal[0][0]=1;
	
	cin>>n;
	for(int i=0;i<n;++i) {
		cin>>a[i]>>b[i];
		lst.push_back(a[i]);
		lst.push_back(b[i]);
	}
	
	sort(all(lst));
	lst.resize(distance(lst.begin(), unique(all(lst))));
	
	int ind=0;
	for(auto i:lst) {
		conv[i]=ind++;
		iconv[ind-1]=i;
	}
	
	for(int i=0;i<n;++i) {
		a[i]=conv[a[i]];
		b[i]=conv[b[i]];
	}
	
	for(int i=0;i<(int)lst.size();++i) {
		for(int j=i;j<(int)lst.size();++j) {
			ways[conv[lst[i]]][conv[lst[j]]]=lst[j]-lst[i]+1;
		}
	}
	
	memset(dp, -1, sizeof dp);
	
	ll ans=-1;
	for(int i=0;i<n;++i) {
		ans+=calc(i, lst.size()-1);
		ans%=mod;
	}
	if(ans<0) ans+=mod;
	
	cout<<ans<<"\n";
	
	
	return 0;
}

• Subtask 1: 0 / 9
• Subtask 2: 0 / 22
• Subtask 3: 0 / 27
• Subtask 4: 0 / 42