Submission #1253027

#	Time	Username	Problem	Language	Result	Execution time	Memory
1253027		nerrrmin	Trains (BOI24_trains)	C++20	58 / 100	170 ms	14204 KiB

Main

#include<bits/stdc++.h>
#define endl '\n'
#define pb push_back
using namespace std;
const long long maxn = 2e5 + 10, maxx = 555;
void speed()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
}
long long n;
long long d[maxn], x[maxn];
vector < long long > g[maxn];
vector < pair < long long, long long > >rem[maxn];
long long dp[maxn], act[maxx][maxx], ans = 0;
const long long mod = 1e9 + 7;

int main()
{
    speed();

    cin >> n;

    long long v;
    for (long long i = 1; i <= n; ++ i)
    {
        cin >> d[i] >> x[i];
        if(!d[i])continue;
        if(d[i] > 400)
        {
            for (int j = 1; j <= x[i]; ++ j)
            {
                int v = i + j * d[i];
                if(v > n)break;
                g[j].pb(i);
            }
        }
        else
        {
            int l = (n - i) / d[i];
            if(l < x[i])x[i] = l;
            rem[i +  x[i] * d[i]].pb(make_pair(d[i], i));
        }
    }

    dp[1] = 1;
    ans = 1;
    if(d[1] && d[1] <= 400)
    {
        act[d[1]][1 % d[1]] += dp[1];
        act[d[1]][1 % d[1]] %= mod;
    }
    if(rem[1].size())
    {
        act[d[1]][1 % d[1]] -= dp[1];
        act[d[1]][1 % d[1]] %= mod;
    }
    for (int i = 2; i <= n; ++ i)
    {

        for (auto e: g[i])
        {
            dp[i] += dp[e];
            dp[i] %= mod;
        }
        for (int r = 1; r <= 400; ++ r)
        {
            int ost = i % r;
            dp[i] += act[r][ost];
            dp[i] %= mod;
        }
        ans += dp[i];
        ans %= mod;

        if(d[i] && d[i] <= 400)
        {
            act[d[i]][i % d[i]] += dp[i];
            act[d[i]][i % d[i]] %= mod;
        }
        for (auto &[prez, j]: rem[i])
        {
            act[prez][j % prez] -= dp[j];
            if(act[prez][j % prez] < 0)act[prez][j % prez] += mod;
        }
    }
    cout << ans << endl;
    return 0;
}

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