Submission #1052867

#	Time	Username	Problem	Language	Result	Execution time	Memory
1052867		vjudge1	Trains (BOI24_trains)	C++17	100 / 100	83 ms	252644 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+500,mod=1e9+7;
const int SQ=317;
ll sm[N][SQ];
ll ways[N],d[N],x[N];
void solve()
{
    ll n;
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        cin>>d[i]>>x[i];
        ways[i]=1;
    }
    for(int i=n;i>=1;i--)
    {
        if(d[i]==0)
        {
            ways[i]=1;
        }
        else{
            if(d[i]<SQ)
            {
                ll j=i+(x[i]*d[i]);
                // maximum x such x<=n and x%d[i] == i%d[i]
                // y = i%d[i]
                //x = k*d + y
                // (k*d) + y <=n 
                // i + (k*d) <= n
                // (k)<= (n-i)/d
                ll ny=(((n-i)/d[i])*d[i]) + i;
                ny=min(ny,j);
                ways[i]=(((sm[i+d[i]][d[i]]-sm[ny+d[i]][d[i]])%mod)+mod)%mod;
                ways[i] = (ways[i]+1)%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[i][j]=(sm[i+j][j]+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: 29 / 29