Submission #1082954

#	Time	Username	Problem	Language	Result	Execution time	Memory
1082954		alexdumitru	Trains (BOI24_trains)	C++17	100 / 100	182 ms	128596 KiB

Main

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

const int NMAX = 1e5;
const int LIM = 320;
const int MOD = 1e9 + 7;

void add(int & x, const int & y) {
    x += y;
    x >= MOD && (x -= MOD);
}

void sub(int & x, const int & y) {
    x -= y;
    x < 0 && (x += MOD);
}

int n;
int d[NMAX + 1], x[NMAX + 1];
int dp[NMAX + 1];
int sumdp[NMAX + 1][LIM];

void read() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> d[i] >> x[i];
    }
}

void solve() {
    for (int i = n; i >= 1; i--) {
        dp[i] = 1;
        if (d[i] >= LIM) {
            for (int pos = i + d[i], cnt = 1; pos <= n && cnt <= x[i]; pos += d[i], cnt++)
                add(dp[i], dp[pos]);
        } else if (d[i] != 0) {
            int nr = min(x[i], (n - i) / d[i]) + 1;
            add(dp[i], sumdp[i + d[i]][d[i]]);
            if (i + nr * d[i] <= n) sub(dp[i], sumdp[i + nr * d[i]][d[i]]);
        }
        for (int m = 1; m < LIM; m++) {
            sumdp[i][m] = i + m <= n ? sumdp[i + m][m] : 0;
            add(sumdp[i][m], dp[i]);
        }
    }
    cout << dp[1] << '\n';
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    read();
    solve();
    return 0;
}

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