oj.uz

Submission #124988

# Submission time Handle Problem Language Result Execution time Memory
124988 2019-07-04T09:46:25 Z Mamnoon_Siam Boat (APIO16_boat) C++17
0 / 100
 13 ms 14328 KB 
#include <bits/stdc++.h>
using namespace std;

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

ll qpow(ll b, ll p) {
	ll ret = 1;
	while(p) {
		if(p & 1) ret = (ret * b) % mod;
		b = (b * b) % mod, p >>= 1;
	} return ret;
}

struct base {
	ll x;
	void fix() {
		if(x < 0 or x >= mod) x %= mod;
		if(x < 0) x += mod;
	}
	base() {x = 0;}
	base(int _x) { x = _x; fix(); }
	base(ll _x) { x = _x; fix(); }
	base operator + (const base &o) const {
		base ret;
		ret.x = x + o.x;
		if(ret.x >= mod) {
			ret.x -= mod;
		}
		return ret;
	}
	base operator * (const base &o) const { return base(x * o.x); }
	base operator / (const base &o) const {
		return base(x * qpow(o.x, mod - 2)); }
	friend ostream& operator << (ostream &out, const base &o) {
		return out << o.x; }
	void operator += (const base &o) { (*this) = (*this) + o; }
	void operator *= (const base &o) { (*this) = (*this) * o; }
};

const int maxn = 505;

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

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

base inv[maxn];
base dp[maxn << 1][maxn];
/* 	dp[rng][i] = # of ways to distribute [1..i] among [1..rng]
 *	ranges s.t. i-th school sends positive amount of boats.
 */
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[])
{
	freopen("in", "r", stdin);
	cin >> n;
	vector<int> tmp;
	for(int i = 1; i <= n; i++) {
		cin >> a[i] >> b[i];
		a[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());

	for(int i = 1; i < tmp.size(); i++) {
		N_rng++;
		l[N_rng] = tmp[i - 1];
		r[N_rng] = tmp[i];
	}

	{ // precalc i^{-1}
		inv[0] = 1;
		for(int i = 1; i <= n; i++) {
			inv[i] = base(1) / i;
		}
	}
	{ // precalc SC[][]
		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++) {
			BC[i][0] = 1;
			for(int j = 1, sz = r[i] - l[i]; j <= n and sz; j++, sz--) {
				BC[i][j] = BC[i][j - 1] * inv[j] * 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[k] <= l[rng] and r[rng] <= b[k]) {
						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

boat.cpp: In function 'int main(int, const char**)':
boat.cpp:74:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 1; i < tmp.size(); i++) {
                 ~~^~~~~~~~~~~~
boat.cpp:61:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("in", "r", stdin);
  ~~~~~~~^~~~~~~~~~~~~~~~~~

Subtask #1
0 / 9.0

# Verdict Execution time Memory Grader output
1 Incorrect 13 ms 14328 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #2
0 / 22.0

# Verdict Execution time Memory Grader output
1 Incorrect 13 ms 14328 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #3
0 / 27.0

# Verdict Execution time Memory Grader output
1 Incorrect 13 ms 14328 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #4
0 / 42.0

# Verdict Execution time Memory Grader output
1 Incorrect 13 ms 14328 KB Output isn't correct
2 Halted 0 ms 0 KB -