Submission #124749

#	Time	Username	Problem	Language	Result	Execution time	Memory
124749		Mamnoon_Siam	Boat (APIO16_boat)	C++17	0 / 100	1221 ms	16376 KiB

boat

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

using ll = long long;
const int mod = 1e9 + 7;

namespace mod_utility {
	const long long mod = 1e9 + 7;
	using ll = long long;
	template <typename dt> inline ll qpow(ll b, dt p) {
		if(p < 0) return qpow(qpow(b, -p), mod - 2);
		long long ret = 1; while(p) {
			if(p & 1) ret = (ret * b) % mod;
			b = (b * b) % mod, p >>= 1;
		} return ret;
	}
	struct base {
		using Int = long long;
		Int x;
		base() {x = 0;}
		base(Int _x) { x = _x; if(x < 0 or x >= mod) fix(); }
		inline void fix() { x %= mod; if(x < 0) x += mod; }
		template <typename dt> inline base pow(dt p) { return base(qpow(x, p)); }
		friend ostream& operator << (ostream &out, const base &p) { return out << p.x; }
		friend istream& operator >> (istream &in, base &p) { return in >> p.x; }
		inline base operator + (const base &that) const { // assuming both are in [0, mod)
			return x + that.x >= mod ? base(x + that.x - mod) : base(x + that.x); }
		inline base operator - (const base &that) const { // assuming both are in [0, mod)
			return x < that.x ? base(x - that.x + mod) : base(x - that.x); }
		inline base operator * (const base &that) const { return base(x * that.x); }
		inline base operator / (const base &that) const { return base(x * qpow(that.x, -1)); }
		inline void operator += (const base &that) { *this = *this + that; }
		inline void operator -= (const base &that) { *this = *this - that; }
		inline void operator *= (const base &that) { *this = *this * that; }
		inline void operator /= (const base &that) { *this = *this / that; }
	};
} using namespace mod_utility;

const int maxn = 505;

base inv[maxn << 1];
base C[maxn][maxn];

base choose(int n, int r) {
	if(r > n or r < 0 or n < 0) return 0;
	base ret = 1;
	for(int i = 1; i <= r; i++, n--) {
		ret *= inv[i] * n;
	} return ret;
}

int n;
int a[maxn], b[maxn];

int N_rng;
int l[maxn << 1], r[maxn << 1];

base dp[maxn << 1][maxn];
base BC[maxn << 1][maxn];	/* BC = nCr for big N = range size, [range][r] */
base SC[maxn][maxn]; 		/* SC = nCr for small N, all pair (N, R) */
base g[maxn << 1][maxn];
/* g[range][k] = \sum{i = 1}^{k} \binom{k - 1}{i - 1} * \binom{range_size}{i} */

int main(int argc, char const *argv[])
{
	cin >> n;
	vector<int> tmp;
	for(int i = 1; i <= n; i++) {
		cin >> a[i] >> b[i];
		tmp.emplace_back(a[i]);
		tmp.emplace_back(b[i]);
	}

	sort(tmp.begin(), tmp.end());
	tmp.erase(unique(tmp.begin(), tmp.end()), tmp.end());
	N_rng = 1;
	l[1] = r[1] = tmp[0];
	for(int i = 1; i < tmp.size(); i++) {
		N_rng++;
		l[N_rng] = tmp[i - 1] + 1;
		r[N_rng] = tmp[i];
	}

	{ // precalc factorial^{-1}
		inv[0] = 1;
		for(int i = 1; i <= n; i++) {
			inv[i] = inv[i - 1] / i;
		}
	}
	{ // precalc C[][]
		for(int i = 0; i <= n; i++) {
			SC[i][0] = 1;
		}
		for(int i = 1; i <= n; i++) {
			for(int j = 1; j <= i; j++) {
				SC[i][j] = SC[i - 1][j] + SC[i - 1][j - 1];
			}
		}
	}
	{ // precalc BC[][]
		for(int i = 1; i <= N_rng; i++) {
			for(int j = 0; j <= n; j++) {
				int sz = r[i] - l[i] + 1;
				if(sz < j) {
					BC[i][j] = 0;
				} else {
					BC[i][j] = 1;
					for(int k = 1; k <= j; k++, sz--) {
						BC[i][j] *= inv[k] * sz;
					}
				}
			}
		}
	}
	{ // precalc g[][]
		for(int range = 1; range <= N_rng; range++) {
			for(int k = 1; k <= n; k++) {
				for(int i = 1; i <= k; i++) {
					g[range][k] += SC[k - 1][i - 1] * BC[range][i];
				}
			}
		}
	}
	for(int i = 0; i <= N_rng; i++) {
		dp[i][0] = 1;
	}
	for(int rng = 1; rng <= N_rng; rng++) {
		for(int i = 1; i <= n; i++) {
			dp[rng][i] = dp[rng - 1][i];
			if(a[i] <= l[rng] and r[rng] <= b[i]) {
				int cnt = 0;
				for(int k = i; k >= 1; k--) {
					if(a[i] <= l[rng] and r[rng] <= b[i]) {
						cnt++;
					}
					dp[rng][i] += dp[rng - 1][k - 1] * g[rng][cnt];
				}
			}
		}
	}
	base ans = 0;
	for(int i = 1; i <= n; i++) {
		ans += dp[N_rng][i];
	}
	cout << ans << endl;
	return 0;
}

Compilation message (stderr)

boat.cpp: In function 'int main(int, const char**)':
boat.cpp:78:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 1; i < tmp.size(); i++) {
                 ~~^~~~~~~~~~~~

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