Submission #1124251

#	Time	Username	Problem	Language	Result	Execution time	Memory
1124251		MateiKing80	Trains (BOI24_trains)	C++20	100 / 100	315 ms	255640 KiB

Main

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

using ll = long long;
#define int ll

const int mod = 1e9 + 7;

#define fr first
#define sc second

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int n;
    cin >> n;
    int b = sqrt(n);
    vector<pair<int, int>> train(n);
    for(int i = 0; i < n; i ++)
    {
        cin >> train[i].fr >> train[i].sc;
        train[i].fr = min(n + 5, train[i].fr);
        train[i].sc = min(n + 5, train[i].sc);
    }
    vector<int> dp(n + 3, 1);
    vector<vector<int>> dp2(n + 3, vector<int>(b + 3, 0));
    for(int i = n - 1; i >= 0; i --)
    {
        if(train[i].fr == 0 || train[i].sc == 0)
        {
            for(int j = 1; j <= b; j ++)
            {
                if(i + j < n)
                    dp2[i][j] = dp2[i + j][j];
                dp2[i][j] += dp[i];
                dp2[i][j] %= mod;
            }
            continue;
        }
        if(train[i].fr >= b)
        {
            for(int j = 1; j <= train[i].sc && train[i].fr * j + i < n; j ++)
            {
                dp[i] += dp[j * train[i].fr + i];
                dp[i] %= mod;
            }
        }
        else
        {
            if(i + train[i].fr < n)
                dp[i] += dp2[i + train[i].fr][train[i].fr];
            if(i + train[i].fr * (train[i].sc + 1) < n)
                dp[i] -= dp2[i + train[i].fr * (train[i].sc + 1)][train[i].fr];
            dp[i] %= mod;
            dp[i] += mod;
            dp[i] %= mod;
        }
        for(int j = 1; j <= b; j ++)
        {
            if(i + j < n)
                dp2[i][j] = dp2[i + j][j];
            dp2[i][j] += dp[i];
            dp2[i][j] %= mod;
        }
    }
    cout << dp[0];
    return 0;
}

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