Submission #733009

#	Time	Username	Problem	Language	Result	Execution time	Memory
733009		SanguineChameleon	Boat (APIO16_boat)	C++17	36 / 100	2059 ms	340 KiB

boat

#include <bits/stdc++.h>
using namespace std;

void just_do_it();

int main() {
	#ifdef KAMIRULEZ
		freopen("kamirulez.inp", "r", stdin);
		freopen("kamirulez.out", "w", stdout);
	#endif
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	just_do_it();
	return 0;
}

const int maxn = 5e2 + 20;
const long long mod = 1e9 + 7;
bool flag[maxn];
long long inv[maxn];
long long fact_inv[maxn];
long long cur[maxn];
long long nxt[maxn];
pair<int, int> events[maxn * 2];
int n;

void trans() {
	for (int i = 1; i <= n; i++) {
		if (flag[i]) {
			nxt[i] = cur[i] + 1;
			if (nxt[i] >= mod) {
				nxt[i] -= mod;
			}
		}
		else {
			nxt[i] = cur[i];
		}
	}
	for (int i = 1; i <= n; i++) {
		for (int j = i + 1; j <= n; j++) {
			if (flag[j]) {
				nxt[j] += cur[i];
				if (nxt[j] >= mod) {
					nxt[j] -= mod;
				}
			}
		}
	}
	swap(cur, nxt);
}

long long choose(int x, int y) {
	if (x < y) {
		return 0;
	}
	long long res = fact_inv[y];
	for (int i = 0; i < y; i++) {
		res = res * (x - i) % mod;
	}
	return res;
}

void shift(int len) {
	for (int i = 1; i <= n; i++) {
		if (flag[i]) {
			nxt[i] = (cur[i] + len) % mod;
		}
		else {
			nxt[i] = cur[i];
		}
	}
	for (int i = 1; i <= n; i++) {
		int cnt = 0;
		for (int j = i + 1; j <= n; j++) {
			if (flag[j]) {
				cnt++;
				if (flag[i]) {
					nxt[j] = (nxt[j] + cur[i] * choose(len + cnt - 1, cnt) + choose(len + cnt - 1, cnt + 1)) % mod;
				}
				else {
					nxt[j] = (nxt[j] + cur[i] * choose(len + cnt - 1, cnt)) % mod;
				}
			}
		}
	}
	swap(cur, nxt);
}

void just_do_it() {
	inv[1] = 1;
	fact_inv[0] = 1;
	fact_inv[1] = 1;
	for (int i = 2; i < maxn; i++) {
		inv[i] = (mod - mod / i) * inv[mod % i] % mod;
		fact_inv[i] = fact_inv[i - 1] * inv[i] % mod;
	}
	cin >> n;
	for (int i = 1; i <= n; i++) {
		int a, b;
		cin >> a >> b;
		events[i * 2 - 1] = make_pair(a, i);
		events[i * 2] = make_pair(b + 1, -i);
	}
	sort(events + 1, events + n * 2 + 1);
	int cur_t = 0;
	for (int i = 1; i <= n * 2; i++) {
		int nxt_t = events[i].first;
		int id = events[i].second;
		bool begin_t = (i == 1 || events[i].first != events[i - 1].first);
		bool end_t = (i == n * 2 || events[i].first != events[i + 1].first);
		if (begin_t) {
			if (cur_t < nxt_t - 1) {
				shift(nxt_t - 1 - cur_t);
				cur_t = nxt_t - 1;
			}
		}
		if (id > 0) {
			flag[id] = true;
		}
		else {
			flag[-id] = false;
		}
		if (end_t && cur_t == nxt_t - 1) {
			trans();
			cur_t = nxt_t;
		}
	}
	long long res = 0;
	for (int i = 1; i <= n; i++) {
		res += cur[i];
		res %= mod;
	}
	cout << res;
}

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