Submission #1052857

#	Time	Username	Problem	Language	Result	Execution time	Memory
1052857		vjudge1	Trains (BOI24_trains)	C++17	71 / 100	2078 ms	6012 KiB

Main

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

#define ll long long
#define vll vector<ll>
#define all(x) begin(x),end(x)
#define pb push_back

const int N=1e5+10,mod=1e9+7;
const int SQ=420;
ll sm[SQ][SQ];
ll ways[N],suf[N],d[N],x[N];
void solve()
{
    ll n;
    cin>>n;
    bool conp=1;
    for(int i=1;i<=n;i++)
    {
        cin>>d[i]>>x[i];
        conp&=(x[i]==1e9);
        ways[i]=1;
    }
    suf[n+1]=0;
    for(int i=n;i>=1;i--)
    {
        if(conp)
        {
            if(d[i]==0)
            {
                ways[i]=1;
            }
            else{
                if(d[i]<SQ)
                {
                    ways[i]=(1+sm[d[i]][i%d[i]])%mod;
                }
                else
                {
                    for(int t=1;t<=x[i] and (i+(d[i]*t))<=n;t++)
                    {
                        ways[i]=(ways[i]+ways[i+(d[i]*t)])%mod;
                    }
                }
                for(int j=1;j<SQ;j++)
                    sm[j][i%j]=(sm[j][i%j]+ways[i])%mod;
            }
        }
        else{
            if(d[i]==1)
            {
                int j=min(n,i+x[i]);
                ways[i] =(((suf[i+1]-suf[j+1])%mod)+mod)%mod;
                ways[i] = (ways[i]+1)%mod;
            }
            else{
                if(d[i]>1){
                    for(int t=1;t<=x[i] and (i+(d[i]*t))<=n;t++)
                    {
                        ways[i]=(ways[i]+ways[i+(d[i]*t)])%mod;
                    }
                }
            }            
            suf[i]=(suf[i+1]+ways[i])%mod;        
        }
    }
    cout<<ways[1]%mod<<endl;
}

int main()
{
	cin.tie(0);cout.tie(0);
	ios::sync_with_stdio(0);
	int t=1;
	// cin>>t;
	while(t--)
		solve();
}

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