Submission #545819

#	Time	Username	Problem	Language	Result	Execution time	Memory
545819		Sohsoh84	Boat (APIO16_boat)	C++17	0 / 100	11 ms	5336 KiB

boat

#include <bits/stdc++.h>

using namespace std;

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

#define all(x)			(x).begin(),(x).end()
#define X			first
#define Y			second
#define sep			' '
#define endl			'\n'
#define debug(x)		cerr << #x << ": " <<  x << endl;

const ll MAXN = 500 + 10;
const ll MOD = 1e9 + 7;

void mkey(int& a) {
	if (a >= MOD) a -= MOD;
}

inline ll poww(ll a, ll b) {
	ll ans = 1;
	while (b) {
		if (b & 1) ans = ans * a % MOD;
		b >>= 1;
		a = a * a % MOD;
	}

	return ans;
}

int n, L[MAXN], R[MAXN], C[MAXN][MAXN], PC[MAXN][MAXN], dp[MAXN][MAXN * 2], 
    ps[2 * MAXN][MAXN], inv[MAXN];
vector<int> vec;

inline int ind(int x) {
	return lower_bound(all(vec), x) - vec.begin();
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> L[i] >> R[i];
		vec.push_back(L[i]);
		vec.push_back(R[i]);
		inv[i] = poww(i, MOD - 2);
	}

	vec.push_back(-1);
	sort(all(vec));
	vec.resize(unique(all(vec)) - vec.begin());

	for (int j = 1; j < int(vec.size()); j++) {
		for (int i = 1; i <= n; i++)
			ps[j][i] = ps[j][i - 1] + (vec[j - 1] < L[i] && R[i] <= vec[j]);
		
		PC[j][0] = C[j][0] = 1;
		int sz = vec[j] - vec[j - 1];
		for (int i = 1; i <= min(sz, n); i++) {
			C[j][i] = 1ll * C[j][i - 1] * (sz - i + 1) % MOD * inv[i] % MOD; 	
			mkey(PC[j][i] = PC[j][i - 1] + C[j][i]);
		}
	}


	fill(dp[0], dp[0] + MAXN, 1);
	int ans = 0;
	for (int i = 1; i <= n; i++) {
		int l = ind(L[i]), r = ind(R[i]);
		for (int j = 1; j < int(vec.size()); j++) {
			int sz = vec[j] - vec[j - 1];
			dp[i][j] = dp[i][j - 1];
			
			if (j >= l && j <= r) {
				for (int k = 0; k < i; k++) {
					dp[i][j] = (dp[i][j] + 1ll * PC[j][min(sz, ps[j][i - 1] - ps[j][k])] * dp[k][j - 1]) % MOD;
				}
			}
		}

		mkey(ans += dp[i][int(vec.size()) - 1]);
	}

	cout << ans << endl;
	return 0;
}

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