Submission #1112502

#	Time	Username	Problem	Language	Result	Execution time	Memory
1112502		gelastropod	Trains (BOI24_trains)	C++14	100 / 100	469 ms	254948 KiB

Main

#include <iostream>
#include <vector>
using namespace std;
#define int long long

signed main(signed argc, char *argv[])
{
	int N, d, x;
	cin >> N;
	vector<vector<int>> prefs;
	vector<int> dp(N, 0);
	for (int i = 0; i * i < N; i++)
		prefs.push_back(vector<int>(N, 0));
	vector<pair<int, int>> vals;
	for (int i = 0; i < N; i++)
	{
		cin >> d >> x;
		vals.push_back({d, x});
	}
	for (int i = N - 1; i >= 0; i--)
	{
		if (vals[i].first == 0)
			dp[i] = 1;
		else if ((vals[i].first - 1) * (vals[i].first - 1) < N)
		{
			if (i + vals[i].first >= N)
				dp[i] = 1;
			else if (i + vals[i].first * (vals[i].second + 1) >= N)
				dp[i] = 1 + prefs[vals[i].first - 1][i + vals[i].first];
			else
				dp[i] = 1 + prefs[vals[i].first - 1][i + vals[i].first] - prefs[vals[i].first - 1][i + vals[i].first * (vals[i].second + 1)];
		}
		else
		{
			dp[i] = 1;
			for (int j = i + vals[i].first, k = 1; j < N && k <= vals[i].second; j += vals[i].first, k++)
				dp[i] += dp[j];
		}
		dp[i] %= 1000000007;
		for (int j = 0; j * j < N; j++)
		{
			if (i + j + 1 < N)
				prefs[j][i] = prefs[j][i + j + 1] + dp[i];
			else
				prefs[j][i] = dp[i];
		}
	}
	cout << dp[0] << '\n';
}

• Subtask 1: 8 / 8
• Subtask 2: 13 / 13
• Subtask 3: 16 / 16
• Subtask 4: 34 / 34
• Subtask 5: 29 / 29