Submission #1130573

#	Time	Username	Problem	Language	Result	Execution time	Memory
1130573		kirakosyan	Trains (BOI24_trains)	C++20	8 / 100	1049 ms	1114112 KiB

Main

#include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<queue>
#include<map>
using namespace std;
using ll = long long;

ll gcd(ll a, ll b)
{
	return b ? gcd(b, a % b) : a;
}
ll mod = 1e9 + 7;
void solve() {
	ll n; cin >> n;
	vector<vector<ll>>gp(n);
	vector<ll>d(n),x(n);
	int f = 0;
	for (ll i = 0; i < n; i++) {
		cin >> d[i] >> x[i];
		if (d[i] != 1)f = 1;
		if (d[i] == 0)continue;
		for (ll j = 1; j <= x[i]; j++) {
			if (i + j * d[i] < n) {
				gp[i].push_back(i + j * d[i]);
			}
			else break;
		}
	}
	 if (f == 0) {
		ll ans = 0;
		vector<ll>pref(n + 10);
		pref[0] = 1;
		 pref[1] = -1;
		for (ll i = 0; i < n; i++) {
			if (i != 0)pref[i] += pref[i - 1];
			pref[i] %= mod;
			pref[i + 1] += pref[i];
			pref[min(n, i + x[i] + 1)] -= pref[i];
			ans += pref[i];
			ans %= mod;
		}
		cout << ans << endl;
	}
	else if (n <= 10000) {
		ll ans = 0;
		vector<ll>dp(n);
		dp[0] = 1;
		for (ll i = 0; i < n; i++) {
			if (dp[i] > mod) dp[i] -= mod;
			for (ll x : gp[i]) {
				dp[x] += dp[i];
				if (dp[x] > mod)dp[x] -= mod;
			}
			ans += dp[i];
			if (ans > mod)ans -= mod;
		}
		cout << ans << endl;
	}


}

signed main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	//signed _; cin >> _; while (_--)
	solve();
}

• Subtask 1: 8 / 8
• Subtask 2: 0 / 13
• Subtask 3: 0 / 16
• Subtask 4: 0 / 34
• Subtask 5: 0 / 29