Submission #376079

#	Time	Username	Problem	Language	Result	Execution time	Memory
376079		shivensinha4	Boat (APIO16_boat)	C++17	36 / 100	1495 ms	24812 KiB

boat

#include "bits/stdc++.h"
using namespace std;
#define for_(i, s, e) for (int i = s; i < (int) e; i++)
#define for__(i, s, e) for (ll i = s; i < e; i++)
typedef long long ll;
typedef vector<int> vi;
typedef array<int, 2> ii;
#define endl '\n'

const ll mod = 1e9+7;

ll power(ll x, ll y) {
	if (y == 0) return 1;
	ll p = power(x, y/2) % mod;
	p = (p * p) % mod;
  
	return (y%2 == 0)? p : (x * p) % mod;
}

ll modInverse(ll a) {
	return power(a, mod-2);
}

const int MXN = 500;
ll choose[2*MXN+2][MXN+1], dp[2][MXN+1][MXN+1][2];

int main() {
#ifdef mlocal
	freopen("test.in", "r", stdin);
#endif
	
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	
	int n; cin >> n;
	vector<ii> lt(n);
	vi raw(2*n);
	
	for_(i, 0, n) {
		cin >> lt[i][0] >> lt[i][1];
		raw[2*i] = lt[i][0], raw[2*i+1] = lt[i][1];
	}
	
	sort(raw.begin(), raw.end());
	raw.resize(unique(raw.begin(), raw.end()) - raw.begin());
	
	vector<ii> seg;
	int pre = -1;
	for_(i, 0, raw.size()) {
		if (pre < raw[i] and pre != -1) seg.push_back({pre, raw[i]-1});
		seg.push_back({raw[i], raw[i]});
		pre = raw[i]+1;
	}
	
	int ns = seg.size();
	memset(choose, 0, sizeof(choose)); memset(dp, 0, sizeof(dp));
	
	for_(i, 0, ns) {
		choose[i][0] = 1;
		for_(r, 1, min(n, seg[i][1]-seg[i][0]+1) + 1) choose[i][r] = (((choose[i][r-1] * (seg[i][1]-seg[i][0]-r+2)) % mod) * modInverse(r)) % mod;
	}
	
	int c = 0;
	for (int s = ns-1; s >= 0; s--) {
		memset(dp[c], 0, sizeof(dp[c]));
		
		for (int ct = min(n-1, seg[s][1]-seg[s][0]+1); ct >= 0; ct--) {
			dp[c][ct][n][0] = choose[s][ct];
			
			for (int idx = n-1; idx >= 0; idx--) {
				if (seg[s][0] >= lt[idx][0] and seg[s][1] <= lt[idx][1]) dp[c][ct][idx][1] += dp[c][ct+1][idx+1][0];
				if (dp[c][ct][idx][1] >= mod) dp[c][ct][idx][1] -= mod;
				
				dp[c][ct][idx][1] += (choose[s][ct] * (s < ns-1 ? dp[1-c][0][idx][1] : 0)) % mod;
				if (dp[c][ct][idx][1] >= mod) dp[c][ct][idx][1] -= mod;
				
				dp[c][ct][idx][0] = (dp[c][ct][idx][1] + dp[c][ct][idx+1][0]) % mod;
			}
		}
		c = 1-c;
	}
	
	cout << (dp[1-c][0][0][0]-1+mod) % mod << endl;
	
}

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