Submission #995315

#	Time	Username	Problem	Language	Result	Execution time	Memory
995315		PagodePaiva	Trains (BOI24_trains)	C++17	42 / 100	83 ms	1952 KiB

Main

#include<bits/stdc++.h>
#pragma GCC optimize("O3")

using namespace std;

const int N = 1e5+10;
const int B = sqrt(N);
int n;
int d[N], x[N], dp[N];
int pref[B][B];
const int mod = 1e9+7;

void calc(int pos){
    if(d[pos] == 0) return;
    int comp = x[pos];
    comp = min(comp, (n-pos)/d[pos]);
    //cout << pos << ' ' << comp << ' ';
    if(comp <= B){
        for(int i = 1;pos+d[pos]*i <= n and i <= comp;i++){
            dp[pos] += dp[pos+d[pos]*i];
            dp[pos] %= mod;
        }
        return;
    }
    else{
        dp[pos] += pref[d[pos]][pos % d[pos]];
        dp[pos] %= mod;
        return;
    }
}

void upd(int pos){
    for(int i = 1;i < B;i++){
        pref[i][pos % i] += dp[pos];
        pref[i][pos % i] %= mod;
    }
    return;
}

int main(){
    ios::sync_with_stdio(false); cin.tie(0);
    cin >> n;
    for(int i = 1;i <= n;i++){
        cin >> d[i] >> x[i];
    }
    for(int i = 1;i <= n;i++){
        dp[i] = 1;
    }
    for(int i = n;i >= 1;i--){
        calc(i);
        upd(i);
    }
    cout << dp[1] << '\n';
    return 0;
}

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