Submission #40745

#	Time	Username	Problem	Language	Result	Execution time	Memory
40745		ssnsarang2023	Boat (APIO16_boat)	C++14	9 / 100	362 ms	2696 KiB

boat

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> ii;

#define SZ(x) ((int)x.size())

const int mod = (int)1e9+7;
const int N = 505;
int n, f[N], g[N], ftmp[N], gtmp[N], a[N], b[N], inv[N], tmp[N], m;
int choose[N][N], nCk[N], nCk2[N], choose1[N][N], choose2[N][N];
vector<int> c;

int mul(int x, int y) {
	x %= mod, y %= mod;
	if (x < 0) x += mod;
	if (y < 0) y += mod;
	ll re = (ll)x * (ll)y % (ll)mod;
	return (int)re;
}

void add(int &x, int y) {
	x += y, x %= mod;
	if (x < 0) x += mod;
}

int fast_pw(int x, int y) {
	if (y == 1) return x % mod;
	if (y == 0) return 1;
	int t = fast_pw(x, y >> 1);
	t = mul(t, t);
	if (y & 1) t = mul(t, x);
	return t;
}

int main() {
	scanf("%d", &n);
	for (int i = 1; i <= n; ++i) {
		scanf("%d%d", &a[i], &b[i]);
		c.push_back(a[i]);
		c.push_back(b[i]);
	}
	sort(c.begin(), c.end());
	c.resize(distance(c.begin(), unique(c.begin(), c.end())));

	for (int i = 0; i <= n; ++i) choose[i][i] = choose[i][0] = 1;
	inv[0] = f[0] = g[0] = 1;
	for (int i = 1; i <= n; ++i) {
		for (int j = 1; j < i; ++j) choose[i][j] = (choose[i - 1][j - 1] + choose[i - 1][j]) % mod;
		inv[i] = mul(inv[i - 1], fast_pw(i, mod - 2));
		g[i] = 1;
	}

	int sz = SZ(c);
	c.push_back(n);
	for (int i = 0; i < sz; ++i) {
		m = 0;
		int total = c[i + 1] - c[i], tmp_mul1 = 1, tmp_mul2 = 1;
		for (int j = 1; j <= n; ++j) {
			if (b[j] == c[i]) ftmp[j] = gtmp[j] = g[j - 1];
			else if (a[j] <= c[i] && c[i] <= b[j]) tmp[++m] = j;
			if (total - j + 1 > 0) {
				tmp_mul1 = mul(tmp_mul1, total - j + 1);
				nCk[j] = mul(tmp_mul1, inv[j]);
			}
			if (total - j > 0) {
				tmp_mul2 = mul(tmp_mul2, total - j);
				nCk2[j] = mul(tmp_mul2, inv[j]);
			}
		}
		if (m > 0) {
			for (int j = 1; j <= n; ++j) add(gtmp[j], gtmp[j - 1]);
			for (int j = 0; j <= m - 2; ++j) {
				int lmt = min(j, total - 2);
				for (int k = 0; k <= lmt; ++k) {
					choose1[j][k] = mul(choose[j][k], nCk[k + 2]);
					choose2[j][k] = mul(choose[j][k], nCk2[k + 2]);
					if (k > 0) add(choose1[j][k], choose1[j][k - 1]);
					if (k > 0) add(choose2[j][k], choose2[j][k - 1]);
				}
			}
			for (int j = m; j > 0; --j) {
				int id = tmp[j];
				add(ftmp[id], mul(nCk[1], g[id - 1]));
				if (total > 1) {
					for (int k = j - 1; k > 0; --k) {
						int mid = j - k - 1, id2 = tmp[k];
						add(ftmp[id], mul(g[id2 - 1], choose1[mid][min(mid, total - 2)]));
						if (total > 2) add(ftmp[id], mul(gtmp[id2 - 1], choose2[mid][min(mid, total - 3)]));
					}
				}
			}
		}
		g[0] = 1;
		for (int i = 1; i <= n; ++i) {
			add(f[i], ftmp[i]);
			g[i] = (g[i - 1] + f[i]) % mod;
			ftmp[i] = gtmp[i] = 0;
		}
	}
	printf("%d", (g[n] - 1 + mod) % mod);
	return 0;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:40:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
                 ^
boat.cpp:42:30: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &a[i], &b[i]);
                              ^

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