Submission #40752

#	Time	Username	Problem	Language	Result	Execution time	Memory
40752		ssnsarang2023	Boat (APIO16_boat)	C++14	100 / 100	474 ms	3820 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;

int fast_pw(int a, int b) {
	int res = 1;
	while (b) {
		if (b & 1) res = 1ll * res * a % mod; 
		a = 1ll * a * a % mod;
		b >>= 1;
	}
	return res;
}

const int N = 505;
int n, f[N], g[N], a[N], b[N], tmp[N], m;
int choose[N][N], len[N*2], lenCk[N*2][N], c1[N];
vector<int> c;

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

int main() {
	scanf("%d", &n);
	for (int i = 1; i <= n; ++i) {
		scanf("%d%d", &a[i], &b[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())));
	int sz = 0;
	for (int i = 0; i < SZ(c) - 1; ++i) {
		len[++sz] = c[i + 1] - c[i];
		lenCk[sz][0] = 1;
		for (int j = 1; j <= min(len[sz], n); ++j) {
			lenCk[sz][j] = 1ll * lenCk[sz][j - 1] * (len[sz] - j + 1) % mod;
			lenCk[sz][j] = 1ll * lenCk[sz][j] * fast_pw(j, mod - 2) % mod;
		}
	}
	for (int i = 0; i <= n; ++i) choose[i][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;
	}
	for (int i = 1; i <= sz; ++i) {
		m = 0;
		for (int j = 1; j <= n; ++j)
			if (a[j] <= c[i - 1] && c[i] <= b[j])
				tmp[++m] = j;
		for (int j = 1; j <= m; ++j) {
			if (j == 1) {
				for (int k = 0; k <= m; ++k) c1[k] = 0;
				c1[1] = len[i];
				for (int k = 2; k <= m; ++k) {
					int s = k - j + 1;
					for (int x = 2; x <= min(s, len[i]); ++x)
						c1[s] = (c1[s] + 1ll * lenCk[i][x] * choose[s - 2][x - 2]) % mod;
				}
			}
			for (int k = j; k <= m; ++k)
				f[k] = (f[k] + 1ll * c1[k- j + 1] * (g[tmp[j] - 1] + 1)) % mod;
		}
		for (int j = 1, cur = 0, k = 1; j <= n; ++j) {
			while (k <= m && tmp[k] == j) cur = (cur + f[k]) % mod, f[k] = 0, ++k;
			g[j] = (g[j] + cur) % mod;
		}
	}
	printf("%d", g[n]);
	return 0;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:34:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
                 ^
boat.cpp:36:30: 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: 22 / 22
• Subtask 3: 27 / 27
• Subtask 4: 42 / 42