Submission #554345

#	Time	Username	Problem	Language	Result	Execution time	Memory
554345		Keshi	Boat (APIO16_boat)	C++17	100 / 100	327 ms	13704 KiB

boat

//In the name of God
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const ll maxn = 1024;
const ll mod = 1e9 + 7;
const ll inf = 1e18;

#define fast_io ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io freopen("input.txt", "r+", stdin);freopen("output.txt", "w+", stdout);
#define pb push_back
#define Mp make_pair
#define F first
#define S second
#define Sz(x) ll((x).size())
#define all(x) (x).begin(), (x).end()

ll pw(ll a, ll b){
	ll c = 1;
	while(b){
		if(b & 1) c = c * a % mod;
		a = a * a % mod;
		b >>= 1;
	}
	return c;
}

int n, a[maxn], b[maxn];
ll pre[maxn][maxn];
vector<int> vec;
vector<pll> g[maxn];

int main(){
	fast_io;

	cin >> n;
	for(int i = 1; i <= n; i++){
		cin >> a[i] >> b[i];
		b[i]++;
		vec.pb(a[i]);
		vec.pb(b[i]);
	}
	vec.pb(0);
	sort(all(vec));
	vec.resize(unique(all(vec)) - vec.begin());
	for(int i = 0; i + 1 < Sz(vec); i++){
		g[i].pb({0, 0});
		int x = vec[i + 1] - vec[i] - 1;
		pre[i][0] = 1;
		for(int j = 1; j < maxn; j++){
			pre[i][j] = pre[i][j - 1] * (x + j) % mod * pw(j, mod - 2) % mod;
		}
	}
	g[0].pb({1, 1});
	for(int i = 1; i <= n; i++){
		ll x = 0;
		for(int j = 0; j < Sz(vec) - 1; j++){
			if(vec[j] < a[i] || b[i] <= vec[j]){
				x = (x + g[j].back().S) % mod;
				continue;
			}
			ll y = x * pre[j][1] % mod;
			for(int k = 0; k < Sz(g[j]); k++){
				y = (y + g[j][Sz(g[j]) - 1 - k].F * pre[j][k + 2]) % mod;
			}
			ll x2 = (x + g[j].back().S) % mod;
			g[j].pb(Mp(x, y));
			x = x2;
		}
	}
	int ans = 0;
	for(int i = 0; i < Sz(vec) - 1; i++){
		ans += g[i].back().S;
		if(ans >= mod) ans -= mod;
	}
	cout << (ans - 1 + mod) % mod << "\n";

	
	return 0;
}

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