Submission #993202

#	Time	Username	Problem	Language	Result	Execution time	Memory
993202		vladilius	Trains (BOI24_trains)	C++17	100 / 100	158 ms	4996 KiB

Main

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pli = pair<ll, int>;
const int mod = 1e9 + 7;

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
    int n; cin>>n;
    vector<int> d(n + 1), x(n + 1);
    for (int i = 1; i <= n; i++){
        cin>>d[i]>>x[i];
    }
    vector<ll> dp(n + 1); dp[1] = 1;
    int sq = (int) sqrt(n);
    vector<vector<ll>> sum(sq, vector<ll>(sq));
    auto recalc = [&](int i){
        for (int f = 1; f < sq; f++){
            dp[i] = (dp[i] + sum[f][i % f]) % mod;
        }
    };
    priority_queue<pli, vector<pli>, greater<pli>> pq;
    auto add = [&](int i){
        recalc(i);
        if (!d[i]) return;
        if (d[i] >= sq){
            for (int j = 1; j <= x[i]; j++){
                ll v = i + 1LL * d[i] * j;
                if (v > n) break;
                dp[v] = (dp[v] + dp[i]) % mod;
            }
            return;
        }
        pq.push({i + 1LL * d[i] * x[i], i});
        sum[d[i]][i % d[i]] += dp[i];
        sum[d[i]][i % d[i]] %= mod;
    };
    for (int i = 1; i <= n; i++){
        add(i);
        while (!pq.empty()){
            auto [v, j] = pq.top();
            if (v > i) break;
            pq.pop();
            sum[d[j]][j % d[j]] -= dp[j];
            sum[d[j]][j % d[j]] %= mod;
        }
    }
    ll out = 0;
    for (int i = 1; i <= n; i++){
        out = (out + dp[i]) % mod;
    }
    cout<<(out + mod) % mod<<"\n";
}

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