Submission #1033610

#TimeUsernameProblemLanguageResultExecution timeMemory
1033610DuongkobeoTrains (BOI24_trains)C++17
21 / 100
2069 ms1788 KiB
#include<bits/stdc++.h>
#define endl "\n"
#define rs resize
#define pb push_back
#define gcd __gcd 
const int mod = 1e9 + 7;
using namespace std;
void solve() {
    int n; cin >> n;
    vector<int> d(n), x(n);
    for (int i = 0; i < n; ++i) cin >> d[i] >> x[i];
    vector<int> v(n + 1, 0);
    v[1] = 1;
    for (int i = 1; i <= n; ++i) {
        if (d[i - 1] > 0 && x[i - 1] > 0) {
            int d_i = d[i - 1];
            int x_i = x[i - 1];
            for (int t = 1; t <= x_i; ++t) {
                int city = i + t * d_i;
                if (city <= n) v[city] = (v[city] + v[i]) % mod;
                else break;
            }
        }
    }
    int res = 0;
    for (int i = 1; i <= n; ++i) res = (res + v[i]) % mod;
    cout << res;
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    // int t; cin >> t;
    // while (t--) 
        solve();
    return 0;
}
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