Submission #111381

#	Time	Username	Problem	Language	Result	Execution time	Memory
111381		diamond_duke	Boat (APIO16_boat)	C++11	100 / 100	752 ms	4572 KiB

boat

#include <algorithm>
#include <cstring>
#include <cstdio>
using ll = long long;
constexpr int MOD = 1e9 + 7;
inline void Add(int &x, int y) { (x += y) >= MOD ? (x -= MOD) : 0; }
inline int quick_pow(int a, int n)
{
	int res = 1;
	while (n)
	{
		if (n & 1)
			res = (ll)res * a % MOD;
		a = (ll)a * a % MOD;
		n >>= 1;
	}
	return res;
}
int lp[505], rp[505], app[1005], dp[1005][505], sum[1005][505], inv[505];
int main()
{
	// freopen("uoj-204.in", "r", stdin);
	int n, cnt = 0;
	scanf("%d", &n);
	for (int i = 0; i < n; i++)
	{
		scanf("%d%d", lp + i, rp + i);
		app[cnt++] = lp[i];
		app[cnt++] = ++rp[i];
	}
	std::sort(app, app + cnt);
	cnt = std::unique(app, app + cnt) - app;
	for (int i = 0; i < n; i++)
	{
		lp[i] = std::lower_bound(app, app + cnt, lp[i]) - app;
		rp[i] = std::lower_bound(app, app + cnt, rp[i]) - app;
	}
	inv[0] = inv[1] = 1;
	for (int i = 2; i <= n; i++)
		inv[i] = (ll)(MOD - MOD / i) * inv[MOD % i] % MOD;
	dp[0][0] = 1;
	for (int i = 0; i < n; i++)
	{
		for (int j = 0; j < cnt; j++)
		{
			for (int k = 0; k <= i; k++)
			{
				sum[j + 1][k] = sum[j][k];
				Add(sum[j + 1][k], dp[j][k]);
			}
		}
		for (int j = lp[i]; j < rp[i]; j++)
		{
			int len = app[j + 1] - app[j], one = 0;
			for (int k = i; k >= 0; k--)
			{
				dp[j][k + 1] = (dp[j][k + 1] + (ll)dp[j][k] * (len - k) % MOD * inv[k + 1]) % MOD;
				Add(one, sum[j][k]);
			}
			dp[j][1] = (dp[j][1] + (ll)one * len) % MOD;
		}
	}
	int ans = MOD - 1;
	for (int i = 0; i < cnt; i++)
	{
		for (int j = 0; j <= n; j++)
			Add(ans, dp[i][j]);
	}
	printf("%d\n", ans);
	return 0;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:24:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
boat.cpp:27:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", lp + i, rp + i);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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