Submission #999302

#	Time	Username	Problem	Language	Result	Execution time	Memory
999302		hengliao	Trains (BOI24_trains)	C++17	100 / 100	145 ms	7764 KiB

Main

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

#define F first
#define S second
#define pb push_back
#define vll vector<ll>
#define pll pair<ll, ll>
typedef long long ll;

const ll mxN=1e5+5;
const ll A=300;
ll dv[A][A];
ll n;
ll dp[mxN];
ll d[mxN], x[mxN];
vll ot[mxN];
const ll mod=1e9+7;

void solve(){
    memset(dp, 0, sizeof(dp));
    memset(dv, 0, sizeof(dv));
	cin>>n;
    for(ll i=0;i<n;i++){
        cin>>d[i]>>x[i];
    }
    ll ans=0;
    dp[0]=1;
    for(ll i=0;i<n;i++){
        for(auto &it:ot[i]){
            dv[d[it]][it%d[it]]-=dp[it];
            dv[d[it]][it%d[it]]%=mod;
            if(dv[d[it]][it%d[it]]<0) dv[d[it]][it%d[it]]+=mod;
        }
        //cout<<i<<' '<<dp[i]<<'\n';
        for(ll j=1;j<A;j++){
            dp[i]+=dv[j][i%j];
            dp[i]%=mod;
        }
        ans+=dp[i];
        //cout<<i<<' '<<dp[i]<<'\n';
        ans%=mod;
        if(d[i]==0) continue;
        if(d[i]>=A){
            for(ll j=1;j<=x[i];j++){
                if(i+d[i]*j>=n) break;
                dp[i+d[i]*j]+=dp[i];
                dp[i+d[i]*j]%=mod;
            }
        }
        else{
            dv[d[i]][i%d[i]]+=dp[i];
            dv[d[i]][i%d[i]]%=mod;
            if(i+d[i]*x[i]+1<n) ot[i+d[i]*x[i]+1].pb(i);
        }
    }
    cout<<ans<<'\n';
}

int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

	solve();
	return 0;
}

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