Submission #995478

#	Time	Username	Problem	Language	Result	Execution time	Memory
995478		12345678	Trains (BOI24_trains)	C++17	34 / 100	110 ms	5172 KiB

Main

#include <bits/stdc++.h>

using namespace std;

const int nx=1e5+5, mod=1e9+7, kx=255;

int n, d[nx], x[nx], qs[kx][kx], dp[nx], res, k=250;
vector<int> rem[nx];

void add(int idx)
{
    if (d[idx]==0) return;
    if (d[idx]>k)
    {
        if (idx+d[idx]>n) return;
        for (int i=idx+d[idx], j=0; j<x[idx]&&i<=n; j++, i+=d[idx]) dp[i]=(dp[i]+dp[idx])%mod;
    }
    else
    {
        qs[d[idx]][idx%d[idx]]=(qs[d[idx]][idx%d[idx]]+dp[idx])%mod;
        if (idx+((long long)x[idx])*d[idx]<=n) rem[idx+x[idx]*d[idx]].push_back(idx); 
    }
}

int main()
{
    cin.tie(NULL)->sync_with_stdio(false);
    cin>>n;
    for (int i=1; i<=n; i++) cin>>d[i]>>x[i];
    dp[1]=1;
    add(1);
    for (int i=2; i<=n; i++)
    {
        for (int j=1; j<=k; j++) dp[i]=(dp[i]+qs[j][i%j])%mod;
        add(i);
        for (auto idx:rem[i]) qs[d[idx]][idx%d[idx]]=(((qs[d[idx]][idx%d[idx]]-dp[idx])%mod)+mod)%mod;
    }
    for (int i=1; i<=n; i++) res=(res+dp[i])%mod;
    cout<<res;
}

/*
7
2 4
0 3
4 2
1 4
1 1
2 1
4 2
*/

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